diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 53eafd7..15df767 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -622,6 +622,7 @@
 
     // -{fsyntax-only,-analyze,emit-ast,S} only run up to the compiler.
   } else if ((FinalPhaseArg = Args.getLastArg(options::OPT_fsyntax_only)) ||
+             (FinalPhaseArg = Args.getLastArg(options::OPT_rewrite_objc)) ||
              (FinalPhaseArg = Args.getLastArg(options::OPT__analyze,
                                               options::OPT__analyze_auto)) ||
              (FinalPhaseArg = Args.getLastArg(options::OPT_emit_ast)) ||
@@ -742,6 +743,8 @@
 
     if (Args.hasArg(options::OPT_fsyntax_only)) {
       return new CompileJobAction(Input, types::TY_Nothing);
+    } else if (Args.hasArg(options::OPT_rewrite_objc)) {
+      return new CompileJobAction(Input, types::TY_RewrittenObjC);
     } else if (Args.hasArg(options::OPT__analyze, options::OPT__analyze_auto)) {
       return new AnalyzeJobAction(Input, types::TY_Plist);
     } else if (Args.hasArg(options::OPT_emit_ast)) {
@@ -1171,8 +1174,10 @@
     return false;
   }
 
-  // Always use clang for precompiling and AST generation, regardless of archs.
-  if (isa<PrecompileJobAction>(JA) || JA.getType() == types::TY_AST)
+  // Always use clang for precompiling, AST generation, and rewriting,
+  // regardless of archs.
+  if (isa<PrecompileJobAction>(JA) || JA.getType() == types::TY_AST ||
+      JA.getType() == types::TY_RewrittenObjC)
     return true;
 
   // Finally, don't use clang if this isn't one of the user specified archs to
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 7bc7875..9e7ec3b 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -676,6 +676,11 @@
       CmdArgs.push_back("-S");
     } else if (JA.getType() == types::TY_AST) {
       CmdArgs.push_back("-emit-pch");
+    } else if (JA.getType() == types::TY_RewrittenObjC) {
+      CmdArgs.push_back("-rewrite-objc");
+    } else {
+      assert(JA.getType() == types::TY_PP_Asm &&
+             "Unexpected output type!");
     }
   }
 
@@ -1325,11 +1330,18 @@
 
 void gcc::Compile::RenderExtraToolArgs(const JobAction &JA,
                                        ArgStringList &CmdArgs) const {
+  const Driver &D = getToolChain().getDriver();
+
   // If -flto, etc. are present then make sure not to force assembly output.
   if (JA.getType() == types::TY_LLVMBC)
     CmdArgs.push_back("-c");
-  else
+  else {
+    if (JA.getType() != types::TY_PP_Asm)
+      D.Diag(clang::diag::err_drv_invalid_gcc_output_type)
+        << getTypeName(JA.getType());
+      
     CmdArgs.push_back("-S");
+  }
 }
 
 void gcc::Assemble::RenderExtraToolArgs(const JobAction &JA,
@@ -1734,6 +1746,9 @@
   else if (Output.getType() == types::TY_AST)
     D.Diag(clang::diag::err_drv_no_ast_support)
       << getToolChain().getTripleString();
+  else if (JA.getType() != types::TY_PP_Asm)
+    D.Diag(clang::diag::err_drv_invalid_gcc_output_type)
+      << getTypeName(JA.getType());
 
   ArgStringList OutputArgs;
   if (Output.getType() != types::TY_PCH) {