diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index b986f7f..ff4af22 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -988,19 +988,21 @@
   // Explicitly error on some things we know we don't support and can't just
   // ignore.
   types::ID InputType = Inputs[0].getType();
-  Arg *Unsupported;
-  if ((Unsupported = Args.getLastArg(options::OPT_MG)) ||
-      (Unsupported = Args.getLastArg(options::OPT_iframework)) ||
-      (Unsupported = Args.getLastArg(options::OPT_fshort_enums)))
-    D.Diag(clang::diag::err_drv_clang_unsupported)
-      << Unsupported->getOption().getName();
-
-  if (types::isCXX(InputType) &&
-      getToolChain().getTriple().getOS() == llvm::Triple::Darwin &&
-      getToolChain().getTriple().getArch() == llvm::Triple::x86) {
-    if ((Unsupported = Args.getLastArg(options::OPT_fapple_kext)))
-      D.Diag(clang::diag::err_drv_clang_unsupported_opt_cxx_darwin_i386)
+  if (!Args.hasArg(options::OPT_fallow_unsupported)) {
+    Arg *Unsupported;
+    if ((Unsupported = Args.getLastArg(options::OPT_MG)) ||
+        (Unsupported = Args.getLastArg(options::OPT_iframework)) ||
+        (Unsupported = Args.getLastArg(options::OPT_fshort_enums)))
+      D.Diag(clang::diag::err_drv_clang_unsupported)
         << Unsupported->getOption().getName();
+
+    if (types::isCXX(InputType) &&
+        getToolChain().getTriple().getOS() == llvm::Triple::Darwin &&
+        getToolChain().getTriple().getArch() == llvm::Triple::x86) {
+      if ((Unsupported = Args.getLastArg(options::OPT_fapple_kext)))
+        D.Diag(clang::diag::err_drv_clang_unsupported_opt_cxx_darwin_i386)
+          << Unsupported->getOption().getName();
+    }
   }
 
   Args.AddAllArgs(CmdArgs, options::OPT_v);