diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index f4cc7deedfc8f2e3caf16c50617154b72d7e4c09..c412ad593d1caa47531c712542857fe6ca36dda0 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -886,7 +886,7 @@ def err_enum_invalid_underlying : Error<
   "non-integral type %0 is an invalid underlying type">;
 def err_enumerator_too_large : Error<
   "enumerator value is not representable in the underlying type %0">;
-def ext_enumerator_too_large : ExtWarn<
+def ext_enumerator_too_large : Extension<
   "enumerator value is not representable in the underlying type %0">,
   InGroup<Microsoft>;
 def err_enumerator_wrapped : Error<