diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 6c3b6d6..c4c5045 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3777,6 +3777,9 @@
       break;
     case tok::kw_bool:
     case tok::kw__Bool:
+      if (Tok.is(tok::kw__Bool) && !getLangOpts().C99)
+        Diag(Tok, diag::ext_c99_feature) << Tok.getName();
+
       if (Tok.is(tok::kw_bool) &&
           DS.getTypeSpecType() != DeclSpec::TST_unspecified &&
           DS.getStorageClassSpec() == DeclSpec::SCS_typedef) {