diff --git a/src/coreclr/src/System.Private.CoreLib/ILLinkTrim.xml b/src/coreclr/src/System.Private.CoreLib/ILLinkTrim.xml
index ff08dc62974c1..77dc30fe2e702 100644
--- a/src/coreclr/src/System.Private.CoreLib/ILLinkTrim.xml
+++ b/src/coreclr/src/System.Private.CoreLib/ILLinkTrim.xml
@@ -55,8 +55,6 @@
     <!-- Accessed via private reflection and by native code. -->
     <type fullname="System.Diagnostics.Tracing.RuntimeEventSource" />
     <type fullname="System.Diagnostics.Tracing.NativeRuntimeEventSource" />
-    <!-- Accessed via reflection in TraceLogging-style EventSource events. -->
-    <type fullname="*f__AnonymousType*" />
     <type fullname="System.Diagnostics.Tracing.PropertyValue/ReferenceTypeHelper`1">
       <!-- Instantiated via reflection -->
       <method name=".ctor" />
diff --git a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs
index fd42fb69b6183..3d774c297e127 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventSource.cs
@@ -2178,9 +2178,8 @@ private unsafe void WriteEventString(string msgString)
                     Keywords = (EventKeywords)unchecked(keywords),
                     Level = level
                 };
-                var msg = new { message = msgString };
-                var tlet = new TraceLoggingEventTypes(EventName, EventTags.None, new Type[] { msg.GetType() });
-                WriteMultiMergeInner(EventName, ref opt, tlet, null, null, msg);
+                var tlet = new TraceLoggingEventTypes(EventName, EventTags.None, new Type[] { typeof(string) });
+                WriteMultiMergeInner(EventName, ref opt, tlet, null, null, msgString);
             }
             else
             {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs
index 0525413ccd956..768a3ad071bd7 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/SimpleTypeInfos.cs
@@ -147,7 +147,11 @@ public override void WriteMetadata(
             string? name,
             EventFieldFormat format)
         {
-            collector.AddNullTerminatedString(name!, Statics.MakeDataType(TraceLoggingDataType.Utf16String, format));
+            // name can be null if the string was used as a top-level object in an event.
+            // In that case, use 'message' as the name of the field.
+            name ??= "message";
+
+            collector.AddNullTerminatedString(name, Statics.MakeDataType(TraceLoggingDataType.Utf16String, format));
         }
 
         public override void WriteData(TraceLoggingDataCollector collector, PropertyValue value)