diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 998ca8a..841a231 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -139,7 +139,7 @@
     Res.push_back("-momit-leaf-frame-pointer");
   if (Opts.OptimizeSize) {
     assert(Opts.OptimizationLevel == 2 && "Invalid options!");
-    Res.push_back("-Os");
+    Opts.OptimizeSize == 1 ? Res.push_back("-Os") : Res.push_back("-Oz");
   } else if (Opts.OptimizationLevel != 0)
     Res.push_back("-O" + llvm::utostr(Opts.OptimizationLevel));
   if (!Opts.MainFileName.empty()) {
@@ -815,8 +815,8 @@
   unsigned DefaultOpt = 0;
   if (IK == IK_OpenCL && !Args.hasArg(OPT_cl_opt_disable))
     DefaultOpt = 2;
-  // -Os implies -O2
-  return Args.hasArg(OPT_Os) ? 2 :
+  // -Os/-Oz implies -O2
+  return (Args.hasArg(OPT_Os) || Args.hasArg (OPT_Oz)) ? 2 :
     Args.getLastArgIntValue(OPT_O, DefaultOpt, Diags);
 }
 
@@ -931,6 +931,7 @@
   Opts.NoCommon = Args.hasArg(OPT_fno_common);
   Opts.NoImplicitFloat = Args.hasArg(OPT_no_implicit_float);
   Opts.OptimizeSize = Args.hasArg(OPT_Os);
+  Opts.OptimizeSize = Args.hasArg(OPT_Oz) ? 2 : Opts.OptimizeSize;
   Opts.SimplifyLibCalls = !(Args.hasArg(OPT_fno_builtin) ||
                             Args.hasArg(OPT_ffreestanding));
   Opts.UnrollLoops = Args.hasArg(OPT_funroll_loops) ||