diff --git a/src/fsharp/vs/IncrementalBuild.fs b/src/fsharp/vs/IncrementalBuild.fs
index eac4d6429872..429eef5859c1 100755
--- a/src/fsharp/vs/IncrementalBuild.fs
+++ b/src/fsharp/vs/IncrementalBuild.fs
@@ -1354,16 +1354,19 @@ type IncrementalBuilder(tcGlobals,frameworkTcImports, nonFrameworkAssemblyInputs
             IncrementalBuilderEventTesting.MRU.Add(IncrementalBuilderEventTesting.IBEParsed filename)
             let input = ParseOneInputFile(tcConfig,lexResourceManager, [], filename ,isLastCompiland,errorLogger,(*retryLocked*)true)
             fileParsed.Trigger (filename)
+            printfn "parse %s" filename
             let result =
                 match input with
                 | Some(ParsedInput.ImplFile (ParsedImplFileInput.ParsedImplFileInput(fileName,isScript,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules,(isLastCompiland,isExe)))) ->
                     let path = Path.GetDirectoryName fileName
                     match seen.TryGetValue qualifiedNameOfFile.Text with
                     | true, paths ->
-                        let qualifiedNameOfFile = deduplicate paths path qualifiedNameOfFile
+                        let qualifiedNameOfFile = deduplicate paths path qualifiedNameOfFile                        
+                        printfn "seen %s -> %s" filename qualifiedNameOfFile.Text
                         let input = ParsedInput.ImplFile(ParsedImplFileInput.ParsedImplFileInput(fileName,isScript,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules,(isLastCompiland,isExe)))
                         Some input
                     | _ ->
+                        printfn "new %s -> %s" filename qualifiedNameOfFile.Text
                         seen.Add(qualifiedNameOfFile.Text,Set.singleton path)
                         input
                 | Some(ParsedInput.SigFile (ParsedSigFileInput.ParsedSigFileInput(fileName,qualifiedNameOfFile,scopedPragmas,hashDirectives,modules))) ->