diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 9b3b5c7..6c3b6d6 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3689,10 +3689,14 @@
                                      DiagID);
       break;
     case tok::kw__Complex:
+      if (!getLangOpts().C99)
+        Diag(Tok, diag::ext_c99_feature) << Tok.getName();
       isInvalid = DS.SetTypeSpecComplex(DeclSpec::TSC_complex, Loc, PrevSpec,
                                         DiagID);
       break;
     case tok::kw__Imaginary:
+      if (!getLangOpts().C99)
+        Diag(Tok, diag::ext_c99_feature) << Tok.getName();
       isInvalid = DS.SetTypeSpecComplex(DeclSpec::TSC_imaginary, Loc, PrevSpec,
                                         DiagID);
       break;