diff --git a/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs b/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs
index 3aa3bea65e1a2..41fe21c197552 100644
--- a/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs
+++ b/src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/LspFileChangeWatcherTests.cs
@@ -66,7 +66,7 @@ public async Task CreatingDirectoryWatchRequestsDirectoryWatch()
 
         var watcher = GetSingleFileWatcher(dynamicCapabilitiesRpcTarget);
 
-        Assert.Equal(tempDirectory.Path, watcher.GlobPattern.Second.BaseUri.First.LocalPath);
+        Assert.Equal(tempDirectory.Path, watcher.GlobPattern.Second.BaseUri.Second.LocalPath);
         Assert.Equal("**/*", watcher.GlobPattern.Second.Pattern);
 
         // Get rid of the registration and it should be gone again
@@ -98,7 +98,7 @@ public async Task CreatingFileWatchRequestsFileWatch()
 
         var watcher = GetSingleFileWatcher(dynamicCapabilitiesRpcTarget);
 
-        Assert.Equal("Z:\\", watcher.GlobPattern.Second.BaseUri.First.LocalPath);
+        Assert.Equal("Z:\\", watcher.GlobPattern.Second.BaseUri.Second.LocalPath);
         Assert.Equal("SingleFile.txt", watcher.GlobPattern.Second.Pattern);
 
         // Get rid of the registration and it should be gone again
diff --git a/src/LanguageServer/Protocol/Protocol/Converters/SumConverter.cs b/src/LanguageServer/Protocol/Protocol/Converters/SumConverter.cs
index d8fb1d10670a9..dd972bc7eb357 100644
--- a/src/LanguageServer/Protocol/Protocol/Converters/SumConverter.cs
+++ b/src/LanguageServer/Protocol/Protocol/Converters/SumConverter.cs
@@ -259,6 +259,13 @@ public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions
 
         var sumValue = value.Value;
 
+        // behavior from DocumentUriConverter
+        if (sumValue is Uri)
+        {
+            writer.WriteStringValue(sumValue.ToString());
+            return;
+        }
+
         if (sumValue != null)
         {
             JsonSerializer.Serialize(writer, sumValue, options);
@@ -288,6 +295,7 @@ private static bool IsTokenCompatibleWithType(ref Utf8JsonReader reader, SumConv
                 break;
             case JsonTokenType.String:
                 isCompatible = unionTypeInfo.Type == typeof(string) ||
+                               unionTypeInfo.Type == typeof(Uri) ||
                                typeof(IStringEnum).IsAssignableFrom(unionTypeInfo.Type);
                 break;
         }
diff --git a/src/LanguageServer/Protocol/Protocol/FileOperations/RelativePattern.cs b/src/LanguageServer/Protocol/Protocol/FileOperations/RelativePattern.cs
index f4d9994a825e9..6126ef4a7c3b7 100644
--- a/src/LanguageServer/Protocol/Protocol/FileOperations/RelativePattern.cs
+++ b/src/LanguageServer/Protocol/Protocol/FileOperations/RelativePattern.cs
@@ -21,7 +21,7 @@ internal class RelativePattern
     /// </summary>
     [JsonPropertyName("baseUri")]
     [JsonRequired]
-    public SumType<Uri, WorkspaceFolder> BaseUri { get; init; }
+    public SumType<WorkspaceFolder, Uri> BaseUri { get; init; }
 
     /// <summary>
     /// The actual glob pattern. See <see href="https://microsoft.github.io/language-server-protocol/specifications/specification-current/#pattern">Glob Pattern</see> for more detail.