diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 77f2a98..fc91e4c 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -914,7 +914,7 @@
   if (Arg *A = Args.getLastArg(options::OPT_funit_at_a_time,
                                options::OPT_fno_unit_at_a_time)) {
     if (A->getOption().matches(options::OPT_fno_unit_at_a_time))
-      D.Diag(clang::diag::err_drv_clang_unsupported) << A->getAsString(Args);
+      D.Diag(clang::diag::warn_drv_clang_unsupported) << A->getAsString(Args);
   }
 
   // Default to -fno-builtin-str{cat,cpy} on Darwin for ARM.