diff --git a/Lex/Preprocessor.cpp b/Lex/Preprocessor.cpp
index fb4628b..a7880fa 100644
--- a/Lex/Preprocessor.cpp
+++ b/Lex/Preprocessor.cpp
@@ -431,7 +431,10 @@
 
 /// EnterMainSourceFile - Enter the specified FileID as the main source file,
 /// which implicitly adds the builting defines etc.
-void Preprocessor::EnterMainSourceFile(unsigned MainFileID) {
+void Preprocessor::EnterMainSourceFile() {
+  
+  unsigned MainFileID = SourceMgr.getMainFileID();
+  
   // Enter the main file source buffer.
   EnterSourceFile(MainFileID, 0);