diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 7410dbe..0862af3 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -962,6 +962,7 @@
   case tok::kw_bool:
   case tok::kw_decltype:
   case tok::kw_typeof:
+  case tok::kw___underlying_type:
     return true;
 
   default: