diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index 68101fc..b3c38f4 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -516,6 +516,10 @@
   // Match the ')'.
   SourceLocation RParenLoc = MatchRHSPunctuation(tok::r_paren, LParenLoc);
 
+  // TypeRep could be null, if it references an invalid typedef.
+  if (!TypeRep)
+    return ExprError();
+
   assert((Exprs.size() == 0 || Exprs.size()-1 == CommaLocs.size())&&
          "Unexpected number of commas!");
   return Actions.ActOnCXXTypeConstructExpr(DS.getSourceRange(), TypeRep,