diff --git a/src/PowerShellEditorServices.Protocol/LanguageServer/Diagnostics.cs b/src/PowerShellEditorServices.Protocol/LanguageServer/Diagnostics.cs
index 116b77c3e..7aa99a69e 100644
--- a/src/PowerShellEditorServices.Protocol/LanguageServer/Diagnostics.cs
+++ b/src/PowerShellEditorServices.Protocol/LanguageServer/Diagnostics.cs
@@ -71,6 +71,11 @@ public class Diagnostic
         /// Gets or sets the diagnostic message.
         /// </summary>
         public string Message { get; set; }
+
+        /// <summary>
+        /// Gets or sets the source of the diagnostic message.
+        /// </summary>
+        public string Source { get; set; }
     }
 }
 
diff --git a/src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs b/src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs
index ae132731b..cfe41c0ba 100644
--- a/src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs
+++ b/src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs
@@ -27,6 +27,7 @@ namespace Microsoft.PowerShell.EditorServices.Protocol.Server
     public class LanguageServer : LanguageServerBase
     {
         private static CancellationTokenSource existingRequestCancellation;
+        private readonly static string DiagnosticSourceName = "PowerShellEditorServices";
 
         private bool profilesLoaded;
         private EditorSession editorSession;
@@ -994,7 +995,9 @@ protected async Task HandleCodeActionRequest(
             {
                 foreach (var diagnostic in codeActionParams.Context.Diagnostics)
                 {
-                    if (markerIndex.TryGetValue(diagnostic.Code, out correction))
+                    if (string.Equals(diagnostic.Source, DiagnosticSourceName, StringComparison.CurrentCultureIgnoreCase) &&
+                        !string.IsNullOrEmpty(diagnostic.Code) &&
+                        markerIndex.TryGetValue(diagnostic.Code, out correction))
                     {
                         codeActionCommands.Add(
                             new CodeActionCommand
@@ -1335,9 +1338,9 @@ private static Diagnostic GetDiagnosticFromMarker(ScriptFileMarker scriptFileMar
                 Severity = MapDiagnosticSeverity(scriptFileMarker.Level),
                 Message = scriptFileMarker.Message,
                 Code = Guid.NewGuid().ToString(),
+                Source = DiagnosticSourceName,
                 Range = new Range
                 {
-                    // TODO: What offsets should I use?
                     Start = new Position
                     {
                         Line = scriptFileMarker.ScriptRegion.StartLineNumber - 1,
diff --git a/src/PowerShellEditorServices/Workspace/Workspace.cs b/src/PowerShellEditorServices/Workspace/Workspace.cs
index db1affd8f..b34471697 100644
--- a/src/PowerShellEditorServices/Workspace/Workspace.cs
+++ b/src/PowerShellEditorServices/Workspace/Workspace.cs
@@ -301,13 +301,15 @@ internal static bool IsPathInMemory(string filePath)
             // When viewing PowerShell files in the Git diff viewer, VS Code
             // sends the contents of the file at HEAD with a URI that starts
             // with 'inmemory'.  Untitled files which have been marked of
-            // type PowerShell have a path starting with 'untitled'.  Files
-            // opened from the find/replace view will be prefixed with
-            // 'private'.
+            // type PowerShell have a path starting with 'untitled'.
             return
                 filePath.StartsWith("inmemory") ||
                 filePath.StartsWith("untitled") ||
-                filePath.StartsWith("private");
+                filePath.StartsWith("private")  ||
+                filePath.StartsWith("git");
+
+            // TODO #342: Remove 'private' and 'git' and then add logic to
+            // throw when any unsupported file URI scheme is encountered.
         }
 
         private string GetBaseFilePath(string filePath)