diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 47234ef..521c90d 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1015,6 +1015,8 @@
       II.getInputArg().renderAsInput(Args, CmdArgs);
   }
 
+  Args.AddAllArgs(CmdArgs, options::OPT_undef);
+
   const char *Exec =
     Args.MakeArgString(getToolChain().GetProgramPath(C, "clang-cc"));
   Dest.addCommand(new Command(JA, Exec, CmdArgs));