diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 3fa76fa1615a..7800fb518944 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -430,7 +430,8 @@ static void InitializePredefinedMacros(Preprocessor &PP,
   // and __DATE__ etc.
   // These should all be defined in the preprocessor according to the
   // current language configuration.
-  DefineBuiltinMacro(Buf, "__STDC__=1");
+  if (!PP.getLangOptions().Microsoft)
+    DefineBuiltinMacro(Buf, "__STDC__=1");
   if (PP.getLangOptions().AsmPreprocessor)
     DefineBuiltinMacro(Buf, "__ASSEMBLER__=1");
   if (PP.getLangOptions().C99 && !PP.getLangOptions().CPlusPlus)