diff --git a/lib/Sema/ParseAST.cpp b/lib/Sema/ParseAST.cpp
index 898b3c2..7cd3989 100644
--- a/lib/Sema/ParseAST.cpp
+++ b/lib/Sema/ParseAST.cpp
@@ -44,7 +44,8 @@
 
   Sema S(PP, Ctx, *Consumer, CompleteTranslationUnit, CompletionConsumer);
   Parser P(PP, S);
-  PP.EnterMainSourceFile();
+  if (PP.EnterMainSourceFile())
+    return;
 
   // Initialize the parser.
   P.Initialize();