diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 73c02d7..65d109e 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -145,7 +145,7 @@
 std::string HeaderSearch::getPrebuiltModuleFileName(StringRef ModuleName,
                                                     bool FileMapOnly) {
   // First check the module name to pcm file map.
-  auto i(HSOpts->PrebuiltModuleFiles.find(std::string(ModuleName)));
+  auto i(HSOpts->PrebuiltModuleFiles.find(ModuleName));
   if (i != HSOpts->PrebuiltModuleFiles.end())
     return i->second;