Index: lib/Frontend/ASTUnit.cpp
===================================================================
--- lib/Frontend/ASTUnit.cpp	(revision 172881)
+++ lib/Frontend/ASTUnit.cpp	(working copy)
@@ -1913,6 +1913,8 @@
   AST->IncludeBriefCommentsInCodeCompletion
     = IncludeBriefCommentsInCodeCompletion;
   AST->Invocation = CI;
+  AST->FileSystemOpts = CI->getFileSystemOpts();
+  AST->FileMgr = new FileManager(AST->FileSystemOpts);
   AST->UserFilesAreVolatile = UserFilesAreVolatile;
   
   // Recover resources if we crash before exiting this method.