Index: lib/LTO/ThinLTOCodeGenerator.cpp
===================================================================
--- lib/LTO/ThinLTOCodeGenerator.cpp
+++ lib/LTO/ThinLTOCodeGenerator.cpp
@@ -535,7 +535,9 @@
 } // end anonymous namespace
 
 void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
-  ThinLTOBuffer Buffer(Data, Identifier);
+  std::string Id =
+      (Twine(Identifier) + "_" + std::to_string(Modules.size())).str();
+  ThinLTOBuffer Buffer(Data, std::move(Id));
   LLVMContext Context;
   StringRef TripleStr;
   ErrorOr<std::string> TripleOrErr = expectedToErrorOrAndEmitErrors(