diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 15c6c4e..1978c01 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -102,7 +102,7 @@
 static cl::opt<bool>
 UseVZeroUpper("x86-use-vzeroupper",
   cl::desc("Minimize AVX to SSE transition penalty"),
-  cl::init(false));
+  cl::init(true));
 
 //===----------------------------------------------------------------------===//
 // Pass Pipeline Configuration