diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index d9ae3ba..0d97709 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -790,7 +790,7 @@
     Builder.defineMacro("__FINITE_MATH_ONLY__", "0");
 
   if (!LangOpts.MSVCCompat) {
-    if (LangOpts.GNUInline)
+    if (LangOpts.GNUInline || LangOpts.CPlusPlus)
       Builder.defineMacro("__GNUC_GNU_INLINE__");
     else
       Builder.defineMacro("__GNUC_STDC_INLINE__");