diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 04f13901e916..3edcf5d654b9 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -155,7 +155,6 @@ static void SetUpDiagnosticLog(DiagnosticOptions *DiagOpts,
           << DiagOpts->DiagnosticLogFile << EC.message();
     } else {
       FileOS->SetUnbuffered();
-      FileOS->SetUseAtomicWrites(true);
       OS = FileOS.get();
       StreamOwner = std::move(FileOS);
     }
diff --git a/clang/lib/Frontend/HeaderIncludeGen.cpp b/clang/lib/Frontend/HeaderIncludeGen.cpp
index 9123d5321fdb..0bc1169ba0a9 100644
--- a/clang/lib/Frontend/HeaderIncludeGen.cpp
+++ b/clang/lib/Frontend/HeaderIncludeGen.cpp
@@ -92,7 +92,6 @@ void clang::AttachHeaderIncludeGen(Preprocessor &PP,
       delete OS;
     } else {
       OS->SetUnbuffered();
-      OS->SetUseAtomicWrites(true);
       OutputFile = OS;
       OwnsOutputFile = true;
     }