Index: lib/Driver/ToolChain.cpp
===================================================================
--- lib/Driver/ToolChain.cpp
+++ lib/Driver/ToolChain.cpp
@@ -74,11 +74,6 @@
     : D(D), Triple(T), Args(Args), CachedRTTIArg(GetRTTIArgument(Args)),
       CachedRTTIMode(CalculateRTTIMode(Args, Triple, CachedRTTIArg)),
       EffectiveTriple() {
-  if (Arg *A = Args.getLastArg(options::OPT_mthread_model))
-    if (!isThreadModelSupported(A->getValue()))
-      D.Diag(diag::err_drv_invalid_thread_model_for_target)
-          << A->getValue() << A->getAsString(Args);
-
   std::string CandidateLibPath = getArchSpecificLibPath();
   if (getVFS().exists(CandidateLibPath))
     getFilePaths().push_back(CandidateLibPath);
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3254,8 +3254,12 @@
   }
 
   CmdArgs.push_back("-mthread-model");
-  if (Arg *A = Args.getLastArg(options::OPT_mthread_model))
+  if (Arg *A = Args.getLastArg(options::OPT_mthread_model)) {
+    if (!getToolChain().isThreadModelSupported(A->getValue()))
+      D.Diag(diag::err_drv_invalid_thread_model_for_target)
+          << A->getValue() << A->getAsString(Args);
     CmdArgs.push_back(A->getValue());
+  }
   else
     CmdArgs.push_back(Args.MakeArgString(getToolChain().getThreadModel()));