diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 2f64071..3da8ba7 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1218,6 +1218,10 @@
 
     if (Args.hasArg(OPT_fno_objc_infer_related_result_type))
       Opts.ObjCInferRelatedResultType = 0;
+    
+    if (Args.hasArg(OPT_fobjc_subscripting_legacy_runtime))
+      Opts.ObjCSubscriptingLegacyRuntime =
+        (Opts.ObjCRuntime.getKind() == ObjCRuntime::FragileMacOSX);
   }
     
   if (Args.hasArg(OPT_fgnu89_inline))