diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 4df7cfd..3d9d131 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -497,6 +497,9 @@
   if (!LangOpts.CharIsSigned)
     Builder.defineMacro("__CHAR_UNSIGNED__");
 
+  if (!TargetInfo::isTypeSigned(TI.getWCharType()))
+    Builder.defineMacro("__WCHAR_UNSIGNED__");
+
   if (!TargetInfo::isTypeSigned(TI.getWIntType()))
     Builder.defineMacro("__WINT_UNSIGNED__");