diff --git a/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala b/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
index a5ea9a032..929a055f3 100644
--- a/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
+++ b/compiler-plugin/src/main/scala/scalapb/compiler/ProtobufGenerator.scala
@@ -720,19 +720,54 @@ class ProtobufGenerator(
     printer.addWithDelimiter(",")(constructorFields(message).map(_.fullString))
   }
 
+  private def usesBaseTypeInBuilder(field: FieldDescriptor) = field.isRequired || field.noBox
+
   def generateBuilder(message: Descriptor)(printer: FunctionalPrinter): FunctionalPrinter = {
     val myFullScalaName = message.scalaType.fullNameWithMaybeRoot(message)
     val requiredFieldMap: Map[FieldDescriptor, Int] =
       message.fields.filter(_.isRequired).zipWithIndex.toMap
-    case class Field(name: String, typeName: String, default: String, accessor: String)
+    case class Field(
+        name: String,
+        targetName: String,
+        typeName: String,
+        default: String,
+        accessor: String,
+        builder: String
+    )
 
     val fields = message.fieldsWithoutOneofs.map { field =>
-      if (!field.isRepeated)
+      if (usesBaseTypeInBuilder(field)) {
+        // To handle custom types that have no default values, we wrap required/no-boxed messages in
+        // Option during parsing. We also apply the type mapper after parsing is complete.
+        if (field.isMessage)
+          Field(
+            s"__${field.scalaName}",
+            field.scalaName.asSymbol,
+            s"_root_.scala.Option[${field.baseSingleScalaTypeName}]",
+            C.None,
+            s"_root_.scala.Some(${toBaseTypeExpr(field)(s"_message__.${field.scalaName.asSymbol}", EnclosingType.None)})",
+            toCustomTypeExpr(field)(
+              s"__${field.scalaName}.getOrElse(${field.getMessageType.scalaType.fullName}.defaultInstance)",
+              EnclosingType.None
+            )
+          )
+        else
+          Field(
+            s"__${field.scalaName}",
+            field.scalaName.asSymbol,
+            field.baseSingleScalaTypeName,
+            defaultValueForGet(field, uncustomized = true),
+            toBaseTypeExpr(field)(s"_message__.${field.scalaName.asSymbol}", EnclosingType.None),
+            toCustomTypeExpr(field)(s"__${field.scalaName}", EnclosingType.None)
+          )
+      } else if (!field.isRepeated)
         Field(
           s"__${field.scalaName}",
+          field.scalaName.asSymbol,
           field.scalaTypeName,
           defaultValueForDefaultInstance(field),
-          s"_message__.${field.scalaName.asSymbol}"
+          s"_message__.${field.scalaName.asSymbol}",
+          s"__${field.scalaName}"
         )
       else {
         val it =
@@ -741,25 +776,31 @@ class ProtobufGenerator(
           else s"_message__.${field.scalaName.asSymbol}"
         Field(
           s"__${field.scalaName}",
+          field.scalaName.asSymbol,
           s"collection.mutable.Builder[${field.singleScalaTypeName}, ${field.scalaTypeName}]",
           field.collection.newBuilder,
-          s"${field.collection.newBuilder} ++= $it"
+          s"${field.collection.newBuilder} ++= $it",
+          s"__${field.scalaName}.result()"
         )
       }
     } ++ message.getRealOneofs.asScala.map { oneof =>
       Field(
         s"__${oneof.scalaName.name}",
+        oneof.scalaName.name.asSymbol,
         oneof.scalaType.fullName,
         oneof.empty.fullName,
-        s"_message__.${oneof.scalaName.nameSymbol}"
+        s"_message__.${oneof.scalaName.nameSymbol}",
+        s"__${oneof.scalaName.name}"
       )
     } ++ (if (message.preservesUnknownFields)
             Seq(
               Field(
                 "`_unknownFields__`",
+                "unknownFields",
                 "_root_.scalapb.UnknownFieldSet.Builder",
                 "null",
-                "new _root_.scalapb.UnknownFieldSet.Builder(_message__.unknownFields)"
+                "new _root_.scalapb.UnknownFieldSet.Builder(_message__.unknownFields)",
+                "if (_unknownFields__ == null) _root_.scalapb.UnknownFieldSet.empty else _unknownFields__.result()"
               )
             )
           else Seq.empty)
@@ -795,20 +836,7 @@ class ProtobufGenerator(
               )
             }.add(s"$myFullScalaName(")
               .indented(
-                _.addWithDelimiter(",")(
-                  (message.fieldsWithoutOneofs ++ message.getOneofs.asScala).map {
-                    case e: FieldDescriptor if e.isRepeated =>
-                      s"  ${e.scalaName.asSymbol} = __${e.scalaName}.result()"
-                    case e: FieldDescriptor =>
-                      s"  ${e.scalaName.asSymbol} = __${e.scalaName}"
-                    case e: OneofDescriptor =>
-                      s"  ${e.scalaName.nameSymbol} = __${e.scalaName.name}"
-                  } ++ (if (message.preservesUnknownFields)
-                          Seq(
-                            "  unknownFields = if (_unknownFields__ == null) _root_.scalapb.UnknownFieldSet.empty else _unknownFields__.result()"
-                          )
-                        else Seq())
-                )
+                _.addWithDelimiter(",")(fields.map(e => s"  ${e.targetName} = ${e.builder}"))
               )
               .add(")")
           )
@@ -851,28 +879,32 @@ class ProtobufGenerator(
       .print(message.fields) { (printer, field) =>
         val p = {
           val newValBase = if (field.isMessage) {
-            val defInstance =
-              s"${field.getMessageType.scalaType.fullNameWithMaybeRoot(message)}.defaultInstance"
-            val baseInstance =
-              if (field.isRepeated) defInstance
-              else {
+            // In 0.10.x we can't simply call any of the new methods that relies on Builder,
+            // since the references message may have been generated using an older version of
+            // ScalaPB.
+            val baseName = field.baseSingleScalaTypeName
+            val read =
+              if (field.isRepeated) s"_root_.scalapb.LiteParser.readMessage[$baseName](_input__)"
+              else if (usesBaseTypeInBuilder(field)) {
+                s"_root_.scala.Some(__${field.scalaName}.fold(_root_.scalapb.LiteParser.readMessage[$baseName](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))"
+              } else {
                 val expr =
                   if (field.isInOneof)
                     s"__${fieldAccessorSymbol(field)}"
                   else s"__${field.scalaName}"
-                val mappedType =
-                  toBaseFieldType(field).apply(expr, field.enclosingType)
+                val mappedType = toBaseFieldType(field).apply(expr, field.enclosingType)
                 if (field.isInOneof || field.supportsPresence)
-                  (mappedType + s".getOrElse($defInstance)")
-                else mappedType
+                  s"$mappedType.fold(_root_.scalapb.LiteParser.readMessage[$baseName](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _))"
+                else s"_root_.scalapb.LiteParser.readMessage[$baseName](_input__, $mappedType)"
               }
-            s"_root_.scalapb.LiteParser.readMessage(_input__, $baseInstance)"
+            read
           } else if (field.isEnum)
             s"${field.getEnumType.scalaType.fullNameWithMaybeRoot(message)}.fromValue(_input__.readEnum())"
           else if (field.getType == Type.STRING) s"_input__.readStringRequireUtf8()"
           else s"_input__.read${Types.capitalizedType(field.getType)}()"
 
-          val newVal = toCustomType(field)(newValBase)
+          val newVal =
+            if (!usesBaseTypeInBuilder(field)) toCustomType(field)(newValBase) else newValBase
 
           val updateOp =
             if (field.supportsPresence) s"__${field.scalaName} = Option($newVal)"
diff --git a/docs/src/main/scala/com/thesamet/docs/json/MyContainer.scala b/docs/src/main/scala/com/thesamet/docs/json/MyContainer.scala
index a8b568dcc..84677fb88 100644
--- a/docs/src/main/scala/com/thesamet/docs/json/MyContainer.scala
+++ b/docs/src/main/scala/com/thesamet/docs/json/MyContainer.scala
@@ -95,7 +95,7 @@ object MyContainer extends scalapb.GeneratedMessageCompanion[com.thesamet.docs.j
         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __myAny = Option(_root_.scalapb.LiteParser.readMessage(_input__, __myAny.getOrElse(com.google.protobuf.any.Any.defaultInstance)))
+            __myAny = Option(__myAny.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.any.Any](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/docs/src/main/scala/scalapb/docs/person/Person.scala b/docs/src/main/scala/scalapb/docs/person/Person.scala
index b5b935242..f6cd34812 100644
--- a/docs/src/main/scala/scalapb/docs/person/Person.scala
+++ b/docs/src/main/scala/scalapb/docs/person/Person.scala
@@ -149,7 +149,7 @@ object Person extends scalapb.GeneratedMessageCompanion[scalapb.docs.person.Pers
           case 16 =>
             __age = _input__.readInt32()
           case 26 =>
-            __addresses += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.docs.person.Person.Address.defaultInstance)
+            __addresses += _root_.scalapb.LiteParser.readMessage[scalapb.docs.person.Person.Address](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/docs/src/main/scala/scalapb/perf/protos/MessageContainer.scala b/docs/src/main/scala/scalapb/perf/protos/MessageContainer.scala
index ee8c82555..200e9451c 100644
--- a/docs/src/main/scala/scalapb/perf/protos/MessageContainer.scala
+++ b/docs/src/main/scala/scalapb/perf/protos/MessageContainer.scala
@@ -119,9 +119,9 @@ object MessageContainer extends scalapb.GeneratedMessageCompanion[scalapb.perf.p
         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __opt = Option(_root_.scalapb.LiteParser.readMessage(_input__, __opt.getOrElse(scalapb.perf.protos.SimpleMessage.defaultInstance)))
+            __opt = Option(__opt.fold(_root_.scalapb.LiteParser.readMessage[scalapb.perf.protos.SimpleMessage](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 18 =>
-            __rep += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.perf.protos.SimpleMessage.defaultInstance)
+            __rep += _root_.scalapb.LiteParser.readMessage[scalapb.perf.protos.SimpleMessage](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/e2e-withjava/src/main/protobuf/custom_types.proto b/e2e-withjava/src/main/protobuf/custom_types.proto
index 2758b4fee..e23934e09 100644
--- a/e2e-withjava/src/main/protobuf/custom_types.proto
+++ b/e2e-withjava/src/main/protobuf/custom_types.proto
@@ -36,6 +36,22 @@ message CustomMessage {
   repeated Name names = 15               [(scalapb.field).type = "com.thesamet.pb.FullName"];
 }
 
+message HasEmail {
+  optional string optional_email = 1              [(scalapb.field).type = "com.thesamet.pb.Email"];
+  required string required_email = 2              [(scalapb.field).type = "com.thesamet.pb.Email"];
+  repeated string repeated_email = 3              [(scalapb.field).type = "com.thesamet.pb.Email"];
+}
+
+message NoBoxEmail {
+  optional string no_box_email   = 1              [(scalapb.field).type = "com.thesamet.pb.Email", (scalapb.field).no_box=true];
+}
+
+message ContainsHasEmail {
+  optional HasEmail optional_has_email = 1;
+  repeated HasEmail repeated_has_email = 2;
+  required HasEmail required_has_email = 3;
+}
+
 message OneofMessage {
   oneof one_of {
     string person_id = 1                 [(scalapb.field).type = "com.thesamet.pb.PersonId"];
diff --git a/e2e-withjava/src/main/scala/com/thesamet/pb/Email.scala b/e2e-withjava/src/main/scala/com/thesamet/pb/Email.scala
new file mode 100644
index 000000000..807baf81e
--- /dev/null
+++ b/e2e-withjava/src/main/scala/com/thesamet/pb/Email.scala
@@ -0,0 +1,16 @@
+package com.thesamet.pb
+
+import scalapb.TypeMapper
+
+case class Email(user: String, domain: String) {
+  override def toString = s"$user@$domain"
+}
+
+object Email {
+  def fromString(s: String) = s.split("@", 2).toSeq match {
+    case Seq(user, domain) => Email(user, domain)
+    case _                   => throw new IllegalArgumentException(s"Expected @ in email. Got: $s")
+  }
+
+  implicit val emailTypeMapper = TypeMapper[String, Email](fromString)(_.toString)
+}
\ No newline at end of file
diff --git a/e2e/src/test/scala/CustomTypesSpec.scala b/e2e/src/test/scala/CustomTypesSpec.scala
index 3e99ad426..7a33996d3 100644
--- a/e2e/src/test/scala/CustomTypesSpec.scala
+++ b/e2e/src/test/scala/CustomTypesSpec.scala
@@ -80,6 +80,27 @@ class CustomTypesSpec extends AnyFlatSpec with Matchers {
     CustomerEvent mustBe a[DomainEventCompanion]
     CustomerEvent.thisIs must be("The companion object")
   }
+
+  "HasEmail" should "serialize and parse valid instances" in {
+    val dm = HasEmail(
+      requiredEmail = Email("foo", "bar")
+    )
+    HasEmail.parseFrom(dm.toByteArray) must be(dm)
+  }
+
+  "NoBoxEmail" should "serialize and parse valid instances" in {
+    val dm = NoBoxEmail(
+      noBoxEmail = Email("foo", "bar")
+    )
+    NoBoxEmail.parseFrom(dm.toByteArray) must be(dm)
+  }
+
+  "ContainsHasEmail" should "serialize and parse valid instances" in {
+    val cem = ContainsHasEmail(
+      requiredHasEmail = HasEmail(requiredEmail = Email("foo", "bar"))
+    )
+    ContainsHasEmail.parseFrom(cem.toByteArray) must be(cem)
+  }
 }
 
 object CustomTypesSpec {
diff --git a/scalapb-runtime/src/main/scala/scalapb/options/FieldOptions.scala b/scalapb-runtime/src/main/scala/scalapb/options/FieldOptions.scala
index ecd1e65de..33f82afb0 100644
--- a/scalapb-runtime/src/main/scala/scalapb/options/FieldOptions.scala
+++ b/scalapb-runtime/src/main/scala/scalapb/options/FieldOptions.scala
@@ -254,7 +254,7 @@ object FieldOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.Fi
           case 26 =>
             __collectionType = Option(_input__.readStringRequireUtf8())
           case 66 =>
-            __collection = Option(_root_.scalapb.LiteParser.readMessage(_input__, __collection.getOrElse(scalapb.options.Collection.defaultInstance)))
+            __collection = Option(__collection.fold(_root_.scalapb.LiteParser.readMessage[scalapb.options.Collection](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 34 =>
             __keyType = Option(_input__.readStringRequireUtf8())
           case 42 =>
diff --git a/scalapb-runtime/src/main/scala/scalapb/options/ScalaPbOptions.scala b/scalapb-runtime/src/main/scala/scalapb/options/ScalaPbOptions.scala
index 5b91720c9..6fd34b405 100644
--- a/scalapb-runtime/src/main/scala/scalapb/options/ScalaPbOptions.scala
+++ b/scalapb-runtime/src/main/scala/scalapb/options/ScalaPbOptions.scala
@@ -619,13 +619,13 @@ object ScalaPbOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.
           case 184 =>
             __javaConversions = Option(_input__.readBool())
           case 146 =>
-            __auxMessageOptions += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.options.ScalaPbOptions.AuxMessageOptions.defaultInstance)
+            __auxMessageOptions += _root_.scalapb.LiteParser.readMessage[scalapb.options.ScalaPbOptions.AuxMessageOptions](_input__)
           case 154 =>
-            __auxFieldOptions += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.options.ScalaPbOptions.AuxFieldOptions.defaultInstance)
+            __auxFieldOptions += _root_.scalapb.LiteParser.readMessage[scalapb.options.ScalaPbOptions.AuxFieldOptions](_input__)
           case 162 =>
-            __auxEnumOptions += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.options.ScalaPbOptions.AuxEnumOptions.defaultInstance)
+            __auxEnumOptions += _root_.scalapb.LiteParser.readMessage[scalapb.options.ScalaPbOptions.AuxEnumOptions](_input__)
           case 178 =>
-            __auxEnumValueOptions += _root_.scalapb.LiteParser.readMessage(_input__, scalapb.options.ScalaPbOptions.AuxEnumValueOptions.defaultInstance)
+            __auxEnumValueOptions += _root_.scalapb.LiteParser.readMessage[scalapb.options.ScalaPbOptions.AuxEnumValueOptions](_input__)
           case 7992 =>
             __testOnlyNoJavaConversions = Option(_input__.readBool())
           case tag =>
@@ -930,7 +930,7 @@ object ScalaPbOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.
             case 10 =>
               __target = Option(_input__.readStringRequireUtf8())
             case 18 =>
-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(scalapb.options.MessageOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[scalapb.options.MessageOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
               if (_unknownFields__ == null) {
                 _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
@@ -1099,7 +1099,7 @@ object ScalaPbOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.
             case 10 =>
               __target = Option(_input__.readStringRequireUtf8())
             case 18 =>
-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(scalapb.options.FieldOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[scalapb.options.FieldOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
               if (_unknownFields__ == null) {
                 _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
@@ -1268,7 +1268,7 @@ object ScalaPbOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.
             case 10 =>
               __target = Option(_input__.readStringRequireUtf8())
             case 18 =>
-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(scalapb.options.EnumOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[scalapb.options.EnumOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
               if (_unknownFields__ == null) {
                 _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
@@ -1437,7 +1437,7 @@ object ScalaPbOptions extends scalapb.GeneratedMessageCompanion[scalapb.options.
             case 10 =>
               __target = Option(_input__.readStringRequireUtf8())
             case 18 =>
-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(scalapb.options.EnumValueOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[scalapb.options.EnumValueOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
               if (_unknownFields__ == null) {
                 _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Api.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Api.scala
index 99e4f0306..1df725df4 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Api.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Api.scala
@@ -278,15 +278,15 @@ object Api extends scalapb.GeneratedMessageCompanion[com.google.protobuf.api.Api
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __methods += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.api.Method.defaultInstance)
+            __methods += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.api.Method](_input__)
           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 34 =>
             __version = _input__.readStringRequireUtf8()
           case 42 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 50 =>
-            __mixins += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.api.Mixin.defaultInstance)
+            __mixins += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.api.Mixin](_input__)
           case 56 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Method.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Method.scala
index 9ca503d17..54fb2d0f0 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Method.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/api/Method.scala
@@ -265,7 +265,7 @@ object Method extends scalapb.GeneratedMessageCompanion[com.google.protobuf.api.
           case 40 =>
             __responseStreaming = _input__.readBool()
           case 50 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 56 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
index 034194276..890e5bed0 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
@@ -181,9 +181,9 @@ object CodeGeneratorRequest extends scalapb.GeneratedMessageCompanion[com.google
           case 18 =>
             __parameter = Option(_input__.readStringRequireUtf8())
           case 122 =>
-            __protoFile += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FileDescriptorProto.defaultInstance)
+            __protoFile += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FileDescriptorProto](_input__)
           case 26 =>
-            __compilerVersion = Option(_root_.scalapb.LiteParser.readMessage(_input__, __compilerVersion.getOrElse(com.google.protobuf.compiler.plugin.Version.defaultInstance)))
+            __compilerVersion = Option(__compilerVersion.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.compiler.plugin.Version](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
index a0ba71b1c..3dd8279c1 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
@@ -152,7 +152,7 @@ object CodeGeneratorResponse extends scalapb.GeneratedMessageCompanion[com.googl
           case 16 =>
             __supportedFeatures = Option(_input__.readUInt64())
           case 122 =>
-            __file += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.compiler.plugin.CodeGeneratorResponse.File.defaultInstance)
+            __file += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.compiler.plugin.CodeGeneratorResponse.File](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/DescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/DescriptorProto.scala
index 87a986798..a985c1420 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/DescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/DescriptorProto.scala
@@ -289,21 +289,21 @@ object DescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.prot
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             __name = Option(_input__.readStringRequireUtf8())
           case 18 =>
-            __field += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
+            __field += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldDescriptorProto](_input__)
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-            __extension += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
+            __extension += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldDescriptorProto](_input__)
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-            __nestedType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.defaultInstance)
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-            __enumType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.defaultInstance)
+            __enumType += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumDescriptorProto](_input__)
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-            __extensionRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.ExtensionRange.defaultInstance)
+            __extensionRange += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.DescriptorProto.ExtensionRange](_input__)
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-            __oneofDecl += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.OneofDescriptorProto.defaultInstance)
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.MessageOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.MessageOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 74 =>
-            __reservedRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.ReservedRange.defaultInstance)
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@@ -494,7 +494,7 @@ object DescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.prot
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-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.ExtensionRangeOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.ExtensionRangeOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumDescriptorProto.scala
index 9d62827ad..e4013bcd3 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumDescriptorProto.scala
@@ -187,11 +187,11 @@ object EnumDescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.
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             __name = Option(_input__.readStringRequireUtf8())
           case 18 =>
-            __value += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumValueDescriptorProto.defaultInstance)
+            __value += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumValueDescriptorProto](_input__)
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.EnumOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 34 =>
-            __reservedRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.EnumReservedRange.defaultInstance)
+            __reservedRange += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumDescriptorProto.EnumReservedRange](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumOptions.scala
index 51eebb49d..f2f9e5fe2 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumOptions.scala
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             __deprecated = Option(_input__.readBool())
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
index df7fa53eb..bb83a4555 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
@@ -135,7 +135,7 @@ object EnumValueDescriptorProto extends scalapb.GeneratedMessageCompanion[com.go
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.EnumValueOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumValueOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueOptions.scala
index 37bfd8c78..bde2db816 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/EnumValueOptions.scala
@@ -123,7 +123,7 @@ object EnumValueOptions extends scalapb.GeneratedMessageCompanion[com.google.pro
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ExtensionRangeOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
index 425e64ca5..98af47560 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldDescriptorProto.scala
index a19e13f84..ea13e49cc 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldDescriptorProto.scala
@@ -339,7 +339,7 @@ object FieldDescriptorProto extends scalapb.GeneratedMessageCompanion[com.google
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           case 66 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.FieldOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldOptions.scala
index 7e16457ae..9d47f45a5 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FieldOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorProto.scala
index ba4083da5..e9ab768b8 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorProto.scala
@@ -354,17 +354,17 @@ object FileDescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.
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-            __messageType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.defaultInstance)
+            __messageType += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.DescriptorProto](_input__)
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-            __enumType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.defaultInstance)
+            __enumType += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumDescriptorProto](_input__)
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-            __service += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.ServiceDescriptorProto.defaultInstance)
+            __service += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.ServiceDescriptorProto](_input__)
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-            __extension += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
+            __extension += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldDescriptorProto](_input__)
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.FileOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FileOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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-            __sourceCodeInfo = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceCodeInfo.getOrElse(com.google.protobuf.descriptor.SourceCodeInfo.defaultInstance)))
+            __sourceCodeInfo = Option(__sourceCodeInfo.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.SourceCodeInfo](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorSet.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorSet.scala
index b625efd22..c682678c1 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorSet.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileDescriptorSet.scala
@@ -99,7 +99,7 @@ object FileDescriptorSet extends scalapb.GeneratedMessageCompanion[com.google.pr
         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __file += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FileDescriptorProto.defaultInstance)
+            __file += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FileDescriptorProto](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileOptions.scala
index c7483858b..939c71c04 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/FileOptions.scala
@@ -561,7 +561,7 @@ object FileOptions extends scalapb.GeneratedMessageCompanion[com.google.protobuf
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/GeneratedCodeInfo.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/GeneratedCodeInfo.scala
index 10eb3afda..674f38e70 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/GeneratedCodeInfo.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/GeneratedCodeInfo.scala
@@ -107,7 +107,7 @@ object GeneratedCodeInfo extends scalapb.GeneratedMessageCompanion[com.google.pr
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           case 0 => _done__ = true
           case 10 =>
-            __annotation += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.GeneratedCodeInfo.Annotation.defaultInstance)
+            __annotation += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.GeneratedCodeInfo.Annotation](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MessageOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MessageOptions.scala
index 3a06b5f0a..9cc157223 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MessageOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MessageOptions.scala
@@ -225,7 +225,7 @@ object MessageOptions extends scalapb.GeneratedMessageCompanion[com.google.proto
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             __mapEntry = Option(_input__.readBool())
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodDescriptorProto.scala
index 688ce730c..0c0d655b1 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodDescriptorProto.scala
@@ -196,7 +196,7 @@ object MethodDescriptorProto extends scalapb.GeneratedMessageCompanion[com.googl
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           case 34 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.MethodOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.MethodOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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             __clientStreaming = Option(_input__.readBool())
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodOptions.scala
index 3161a5aa5..df157ac76 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/MethodOptions.scala
@@ -146,7 +146,7 @@ object MethodOptions extends scalapb.GeneratedMessageCompanion[com.google.protob
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           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofDescriptorProto.scala
index c501a90f9..ef1de513d 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofDescriptorProto.scala
@@ -116,7 +116,7 @@ object OneofDescriptorProto extends scalapb.GeneratedMessageCompanion[com.google
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           case 18 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.OneofOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.OneofOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofOptions.scala
index 7fb24bda5..a939f8c55 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/OneofOptions.scala
@@ -99,7 +99,7 @@ object OneofOptions extends scalapb.GeneratedMessageCompanion[com.google.protobu
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           case 0 => _done__ = true
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceDescriptorProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceDescriptorProto.scala
index a8789b2e5..bfb19bb72 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceDescriptorProto.scala
@@ -137,9 +137,9 @@ object ServiceDescriptorProto extends scalapb.GeneratedMessageCompanion[com.goog
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             __name = Option(_input__.readStringRequireUtf8())
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-            __method += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.MethodDescriptorProto.defaultInstance)
+            __method += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.MethodDescriptorProto](_input__)
           case 26 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.ServiceOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.ServiceOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceOptions.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceOptions.scala
index 1711e2585..bb6d5f41d 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceOptions.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/ServiceOptions.scala
@@ -123,7 +123,7 @@ object ServiceOptions extends scalapb.GeneratedMessageCompanion[com.google.proto
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             __deprecated = Option(_input__.readBool())
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/SourceCodeInfo.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/SourceCodeInfo.scala
index 29fb87d87..5344dc59b 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/SourceCodeInfo.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/SourceCodeInfo.scala
@@ -147,7 +147,7 @@ object SourceCodeInfo extends scalapb.GeneratedMessageCompanion[com.google.proto
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           case 0 => _done__ = true
           case 10 =>
-            __location += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.SourceCodeInfo.Location.defaultInstance)
+            __location += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.SourceCodeInfo.Location](_input__)
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/UninterpretedOption.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/UninterpretedOption.scala
index 2c98bfc9f..184d0028a 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/UninterpretedOption.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/descriptor/UninterpretedOption.scala
@@ -212,7 +212,7 @@ object UninterpretedOption extends scalapb.GeneratedMessageCompanion[com.google.
         _tag__ match {
           case 0 => _done__ = true
           case 18 =>
-            __name += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.NamePart.defaultInstance)
+            __name += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption.NamePart](_input__)
           case 26 =>
             __identifierValue = Option(_input__.readStringRequireUtf8())
           case 32 =>
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/ListValue.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/ListValue.scala
index 2e3362ad1..d0f3bfa67 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/ListValue.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/ListValue.scala
@@ -103,7 +103,7 @@ object ListValue extends scalapb.GeneratedMessageCompanion[com.google.protobuf.s
         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __values += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.struct.Value.defaultInstance)
+            __values += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Value](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Struct.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Struct.scala
index 3f76d3e2c..6231b979f 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Struct.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Struct.scala
@@ -111,7 +111,7 @@ object Struct extends scalapb.GeneratedMessageCompanion[com.google.protobuf.stru
         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __fields += com.google.protobuf.struct.Struct._typemapper_fields.toCustom(_root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.struct.Struct.FieldsEntry.defaultInstance))
+            __fields += com.google.protobuf.struct.Struct._typemapper_fields.toCustom(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Struct.FieldsEntry](_input__))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
@@ -255,7 +255,7 @@ object Struct extends scalapb.GeneratedMessageCompanion[com.google.protobuf.stru
             case 10 =>
               __key = _input__.readStringRequireUtf8()
             case 18 =>
-              __value = Option(_root_.scalapb.LiteParser.readMessage(_input__, __value.getOrElse(com.google.protobuf.struct.Value.defaultInstance)))
+              __value = Option(__value.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Value](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
               if (_unknownFields__ == null) {
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Value.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Value.scala
index d9b2cd840..3bee75715 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Value.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/struct/Value.scala
@@ -184,9 +184,9 @@ object Value extends scalapb.GeneratedMessageCompanion[com.google.protobuf.struc
           case 32 =>
             __kind = com.google.protobuf.struct.Value.Kind.BoolValue(_input__.readBool())
           case 42 =>
-            __kind = com.google.protobuf.struct.Value.Kind.StructValue(_root_.scalapb.LiteParser.readMessage(_input__, __kind.structValue.getOrElse(com.google.protobuf.struct.Struct.defaultInstance)))
+            __kind = com.google.protobuf.struct.Value.Kind.StructValue(__kind.structValue.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Struct](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 50 =>
-            __kind = com.google.protobuf.struct.Value.Kind.ListValue(_root_.scalapb.LiteParser.readMessage(_input__, __kind.listValue.getOrElse(com.google.protobuf.struct.ListValue.defaultInstance)))
+            __kind = com.google.protobuf.struct.Value.Kind.ListValue(__kind.listValue.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.ListValue](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Enum.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Enum.scala
index a15f7ff0d..074baad29 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Enum.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Enum.scala
@@ -202,11 +202,11 @@ object Enum extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type`
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __enumvalue += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.EnumValue.defaultInstance)
+            __enumvalue += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.EnumValue](_input__)
           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 34 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 40 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/EnumValue.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/EnumValue.scala
index 1d7ca9e58..5b4d10a1d 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/EnumValue.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/EnumValue.scala
@@ -155,7 +155,7 @@ object EnumValue extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`
           case 16 =>
             __number = _input__.readInt32()
           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Field.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Field.scala
index b46a18a84..0752a8001 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Field.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Field.scala
@@ -347,7 +347,7 @@ object Field extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type
           case 64 =>
             __packed = _input__.readBool()
           case 74 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 82 =>
             __jsonName = _input__.readStringRequireUtf8()
           case 90 =>
diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/OptionProto.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/OptionProto.scala
index cfc27d4b1..0dc8adaf5 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/OptionProto.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/OptionProto.scala
@@ -134,7 +134,7 @@ object OptionProto extends scalapb.GeneratedMessageCompanion[com.google.protobuf
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __value = Option(_root_.scalapb.LiteParser.readMessage(_input__, __value.getOrElse(com.google.protobuf.any.Any.defaultInstance)))
+            __value = Option(__value.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.any.Any](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
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diff --git a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Type.scala b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Type.scala
index ff505ea76..651434edf 100644
--- a/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Type.scala
+++ b/scalapb-runtime/src/main/scalajs/com/google/protobuf/type/Type.scala
@@ -222,13 +222,13 @@ object Type extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type`
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __fields += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.Field.defaultInstance)
+            __fields += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.Field](_input__)
           case 26 =>
             __oneofs += _input__.readStringRequireUtf8()
           case 34 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 42 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 48 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Api.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Api.scala
index 97256407c..f58b5c604 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Api.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Api.scala
@@ -299,15 +299,15 @@ object Api extends scalapb.GeneratedMessageCompanion[com.google.protobuf.api.Api
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __methods += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.api.Method.defaultInstance)
+            __methods += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.api.Method](_input__)
           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 34 =>
             __version = _input__.readStringRequireUtf8()
           case 42 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 50 =>
-            __mixins += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.api.Mixin.defaultInstance)
+            __mixins += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.api.Mixin](_input__)
           case 56 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Method.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Method.scala
index 26615da2f..287be98fe 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Method.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/api/Method.scala
@@ -286,7 +286,7 @@ object Method extends scalapb.GeneratedMessageCompanion[com.google.protobuf.api.
           case 40 =>
             __responseStreaming = _input__.readBool()
           case 50 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 56 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
index 0f5a68ff9..871d3ea9e 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorRequest.scala
@@ -196,9 +196,9 @@ object CodeGeneratorRequest extends scalapb.GeneratedMessageCompanion[com.google
           case 18 =>
             __parameter = Option(_input__.readStringRequireUtf8())
           case 122 =>
-            __protoFile += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FileDescriptorProto.defaultInstance)
+            __protoFile += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FileDescriptorProto](_input__)
           case 26 =>
-            __compilerVersion = Option(_root_.scalapb.LiteParser.readMessage(_input__, __compilerVersion.getOrElse(com.google.protobuf.compiler.plugin.Version.defaultInstance)))
+            __compilerVersion = Option(__compilerVersion.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.compiler.plugin.Version](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
index 4693ac229..c4c866c9e 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/compiler/plugin/CodeGeneratorResponse.scala
@@ -165,7 +165,7 @@ object CodeGeneratorResponse extends scalapb.GeneratedMessageCompanion[com.googl
           case 16 =>
             __supportedFeatures = Option(_input__.readUInt64())
           case 122 =>
-            __file += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.compiler.plugin.CodeGeneratorResponse.File.defaultInstance)
+            __file += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.compiler.plugin.CodeGeneratorResponse.File](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/DescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/DescriptorProto.scala
index 1de62e154..8653cc1a4 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/DescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/DescriptorProto.scala
@@ -316,21 +316,21 @@ object DescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.prot
           case 10 =>
             __name = Option(_input__.readStringRequireUtf8())
           case 18 =>
-            __field += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
+            __field += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldDescriptorProto](_input__)
           case 50 =>
-            __extension += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
+            __extension += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.FieldDescriptorProto](_input__)
           case 26 =>
-            __nestedType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.defaultInstance)
+            __nestedType += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.DescriptorProto](_input__)
           case 34 =>
-            __enumType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.defaultInstance)
+            __enumType += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumDescriptorProto](_input__)
           case 42 =>
-            __extensionRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.ExtensionRange.defaultInstance)
+            __extensionRange += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.DescriptorProto.ExtensionRange](_input__)
           case 66 =>
-            __oneofDecl += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.OneofDescriptorProto.defaultInstance)
+            __oneofDecl += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.OneofDescriptorProto](_input__)
           case 58 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.MessageOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.MessageOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 74 =>
-            __reservedRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.DescriptorProto.ReservedRange.defaultInstance)
+            __reservedRange += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.DescriptorProto.ReservedRange](_input__)
           case 82 =>
             __reservedName += _input__.readStringRequireUtf8()
           case tag =>
@@ -533,7 +533,7 @@ object DescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.prot
             case 16 =>
               __end = Option(_input__.readInt32())
             case 26 =>
-              __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.ExtensionRangeOptions.defaultInstance)))
+              __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.ExtensionRangeOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
             case tag =>
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumDescriptorProto.scala
index d65bc27bd..8051de6c9 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumDescriptorProto.scala
@@ -204,11 +204,11 @@ object EnumDescriptorProto extends scalapb.GeneratedMessageCompanion[com.google.
           case 10 =>
             __name = Option(_input__.readStringRequireUtf8())
           case 18 =>
-            __value += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumValueDescriptorProto.defaultInstance)
+            __value += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumValueDescriptorProto](_input__)
           case 26 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.EnumOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 34 =>
-            __reservedRange += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.EnumReservedRange.defaultInstance)
+            __reservedRange += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumDescriptorProto.EnumReservedRange](_input__)
           case 42 =>
             __reservedName += _input__.readStringRequireUtf8()
           case tag =>
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumOptions.scala
index 60120fa7c..7606a12d3 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumOptions.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumOptions.scala
@@ -158,7 +158,7 @@ object EnumOptions extends scalapb.GeneratedMessageCompanion[com.google.protobuf
           case 24 =>
             __deprecated = Option(_input__.readBool())
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
index 5387fef5d..81de0d7da 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueDescriptorProto.scala
@@ -147,7 +147,7 @@ object EnumValueDescriptorProto extends scalapb.GeneratedMessageCompanion[com.go
           case 16 =>
             __number = Option(_input__.readInt32())
           case 26 =>
-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.EnumValueOptions.defaultInstance)))
+            __options = Option(__options.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.EnumValueOptions](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueOptions.scala
index 3c8faf302..f1192d4fc 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueOptions.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/EnumValueOptions.scala
@@ -134,7 +134,7 @@ object EnumValueOptions extends scalapb.GeneratedMessageCompanion[com.google.pro
           case 8 =>
             __deprecated = Option(_input__.readBool())
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ExtensionRangeOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
index 390a14b02..5d61b77e3 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ExtensionRangeOptions.scala
@@ -108,7 +108,7 @@ object ExtensionRangeOptions extends scalapb.GeneratedMessageCompanion[com.googl
         _tag__ match {
           case 0 => _done__ = true
           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldDescriptorProto.scala
index 43c61e7ef..001409d10 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldDescriptorProto.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldDescriptorProto.scala
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.FieldOptions.defaultInstance)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldOptions.scala
index 063b901f0..3f1e80441 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FieldOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorProto.scala
index 1fdcc42b0..569f06fac 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorProto.scala
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-            __enumType += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.EnumDescriptorProto.defaultInstance)
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-            __service += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.ServiceDescriptorProto.defaultInstance)
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-            __extension += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FieldDescriptorProto.defaultInstance)
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.FileOptions.defaultInstance)))
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-            __sourceCodeInfo = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceCodeInfo.getOrElse(com.google.protobuf.descriptor.SourceCodeInfo.defaultInstance)))
+            __sourceCodeInfo = Option(__sourceCodeInfo.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.SourceCodeInfo](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorSet.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorSet.scala
index 9abaee528..2d30b3057 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileDescriptorSet.scala
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           case 10 =>
-            __file += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.FileDescriptorProto.defaultInstance)
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index f29ed7365..d5e2201e2 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/FileOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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index 2b831b6f2..0a8cedbde 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/GeneratedCodeInfo.scala
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-            __annotation += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.GeneratedCodeInfo.Annotation.defaultInstance)
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index 982716736..b8bbf13f0 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/MessageOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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index e73311c87..911d8c9c5 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/MethodDescriptorProto.scala
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.MethodOptions.defaultInstance)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/MethodOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/MethodOptions.scala
index db0414956..58b084334 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/MethodOptions.scala
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-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofDescriptorProto.scala
index a10d8b674..f1c16e1f8 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofDescriptorProto.scala
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.OneofOptions.defaultInstance)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofOptions.scala
index 312eff9cc..4b9fbdb27 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofOptions.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/OneofOptions.scala
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           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceDescriptorProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceDescriptorProto.scala
index d09041ed2..ca26a2dc4 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceDescriptorProto.scala
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@@ -150,9 +150,9 @@ object ServiceDescriptorProto extends scalapb.GeneratedMessageCompanion[com.goog
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-            __method += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.MethodDescriptorProto.defaultInstance)
+            __method += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.MethodDescriptorProto](_input__)
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-            __options = Option(_root_.scalapb.LiteParser.readMessage(_input__, __options.getOrElse(com.google.protobuf.descriptor.ServiceOptions.defaultInstance)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceOptions.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceOptions.scala
index 253ac2cc6..1a92c4c33 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/ServiceOptions.scala
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           case 7994 =>
-            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.defaultInstance)
+            __uninterpretedOption += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/SourceCodeInfo.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/SourceCodeInfo.scala
index eb3c66556..ce81fe5f2 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/SourceCodeInfo.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/SourceCodeInfo.scala
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-            __location += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.SourceCodeInfo.Location.defaultInstance)
+            __location += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.SourceCodeInfo.Location](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/UninterpretedOption.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/UninterpretedOption.scala
index 4daa531ae..d7930471f 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/UninterpretedOption.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/descriptor/UninterpretedOption.scala
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           case 18 =>
-            __name += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.descriptor.UninterpretedOption.NamePart.defaultInstance)
+            __name += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.descriptor.UninterpretedOption.NamePart](_input__)
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             __identifierValue = Option(_input__.readStringRequireUtf8())
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/ListValue.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/ListValue.scala
index 7ec68222d..0dfba9b2e 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/ListValue.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/ListValue.scala
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         _tag__ match {
           case 0 => _done__ = true
           case 10 =>
-            __values += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.struct.Value.defaultInstance)
+            __values += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Value](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Struct.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Struct.scala
index 1a54ab6fc..2a114a36b 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Struct.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Struct.scala
@@ -123,7 +123,7 @@ object Struct extends scalapb.GeneratedMessageCompanion[com.google.protobuf.stru
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           case 10 =>
-            __fields += com.google.protobuf.struct.Struct._typemapper_fields.toCustom(_root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.struct.Struct.FieldsEntry.defaultInstance))
+            __fields += com.google.protobuf.struct.Struct._typemapper_fields.toCustom(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Struct.FieldsEntry](_input__))
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@@ -267,7 +267,7 @@ object Struct extends scalapb.GeneratedMessageCompanion[com.google.protobuf.stru
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             case 18 =>
-              __value = Option(_root_.scalapb.LiteParser.readMessage(_input__, __value.getOrElse(com.google.protobuf.struct.Value.defaultInstance)))
+              __value = Option(__value.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Value](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Value.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Value.scala
index f14ec33d1..3d93daa73 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Value.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/struct/Value.scala
@@ -205,9 +205,9 @@ object Value extends scalapb.GeneratedMessageCompanion[com.google.protobuf.struc
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-            __kind = com.google.protobuf.struct.Value.Kind.StructValue(_root_.scalapb.LiteParser.readMessage(_input__, __kind.structValue.getOrElse(com.google.protobuf.struct.Struct.defaultInstance)))
+            __kind = com.google.protobuf.struct.Value.Kind.StructValue(__kind.structValue.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.Struct](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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-            __kind = com.google.protobuf.struct.Value.Kind.ListValue(_root_.scalapb.LiteParser.readMessage(_input__, __kind.listValue.getOrElse(com.google.protobuf.struct.ListValue.defaultInstance)))
+            __kind = com.google.protobuf.struct.Value.Kind.ListValue(__kind.listValue.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.struct.ListValue](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Enum.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Enum.scala
index 9d1ce9e95..e3f37e1ad 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Enum.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Enum.scala
@@ -219,11 +219,11 @@ object Enum extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type`
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             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __enumvalue += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.EnumValue.defaultInstance)
+            __enumvalue += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.EnumValue](_input__)
           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 34 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/EnumValue.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/EnumValue.scala
index f62558ded..7ea9afc64 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/EnumValue.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/EnumValue.scala
@@ -168,7 +168,7 @@ object EnumValue extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`
           case 16 =>
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           case 26 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Field.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Field.scala
index b08c227d4..13b5cfe8d 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Field.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Field.scala
@@ -374,7 +374,7 @@ object Field extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type
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           case 74 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
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diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/OptionProto.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/OptionProto.scala
index c086ad900..bb03a5a49 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/OptionProto.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/OptionProto.scala
@@ -144,7 +144,7 @@ object OptionProto extends scalapb.GeneratedMessageCompanion[com.google.protobuf
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __value = Option(_root_.scalapb.LiteParser.readMessage(_input__, __value.getOrElse(com.google.protobuf.any.Any.defaultInstance)))
+            __value = Option(__value.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.any.Any](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case tag =>
             if (_unknownFields__ == null) {
               _unknownFields__ = new _root_.scalapb.UnknownFieldSet.Builder()
diff --git a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Type.scala b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Type.scala
index abfac6b16..257dd0e9c 100644
--- a/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Type.scala
+++ b/scalapb-runtime/src/main/scalajvm/com/google/protobuf/type/Type.scala
@@ -241,13 +241,13 @@ object Type extends scalapb.GeneratedMessageCompanion[com.google.protobuf.`type`
           case 10 =>
             __name = _input__.readStringRequireUtf8()
           case 18 =>
-            __fields += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.Field.defaultInstance)
+            __fields += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.Field](_input__)
           case 26 =>
             __oneofs += _input__.readStringRequireUtf8()
           case 34 =>
-            __options += _root_.scalapb.LiteParser.readMessage(_input__, com.google.protobuf.`type`.OptionProto.defaultInstance)
+            __options += _root_.scalapb.LiteParser.readMessage[com.google.protobuf.`type`.OptionProto](_input__)
           case 42 =>
-            __sourceContext = Option(_root_.scalapb.LiteParser.readMessage(_input__, __sourceContext.getOrElse(com.google.protobuf.source_context.SourceContext.defaultInstance)))
+            __sourceContext = Option(__sourceContext.fold(_root_.scalapb.LiteParser.readMessage[com.google.protobuf.source_context.SourceContext](_input__))(_root_.scalapb.LiteParser.readMessage(_input__, _)))
           case 48 =>
             __syntax = com.google.protobuf.`type`.Syntax.fromValue(_input__.readEnum())
           case tag =>