diff --git a/llvm/lib/Target/X86/X86InstrInfo.h b/llvm/lib/Target/X86/X86InstrInfo.h
index 39448cabb499..4625b4c986ab 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.h
+++ b/llvm/lib/Target/X86/X86InstrInfo.h
@@ -449,7 +449,7 @@ namespace X86II {
     SSEDomainShift = SegOvrShift + 2,
 
     OpcodeShift   = SSEDomainShift + 2,
-    OpcodeMask    = 0xFF << OpcodeShift,
+    OpcodeMask    = 0xFFULL << OpcodeShift,
 
     //===------------------------------------------------------------------===//
     /// VEX - The opcode prefix used by AVX instructions