diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 3fdbc16..9ad4145 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -583,6 +583,8 @@
     Res.push_back("-fsjlj-exceptions");
   if (!Opts.RTTI)
     Res.push_back("-fno-rtti");
+  if (Opts.MSBitfields)
+    Res.push_back("-mms-bitfields");
   if (!Opts.NeXTRuntime)
     Res.push_back("-fgnu-runtime");
   if (Opts.Freestanding)
@@ -1445,6 +1447,7 @@
                                                Diags);
   Opts.NumLargeByValueCopy = Args.getLastArgIntValue(OPT_Wlarge_by_value_copy,
                                                     0, Diags);
+  Opts.MSBitfields = Args.hasArg(OPT_mms_bitfields);
   Opts.NeXTRuntime = !Args.hasArg(OPT_fgnu_runtime);
   Opts.ObjCConstantStringClass =
     Args.getLastArgValue(OPT_fconstant_string_class);