diff --git a/arch/X86/X86DisassemblerDecoder.c b/arch/X86/X86DisassemblerDecoder.c
index bb460e7b..e13482fa 100644
--- a/arch/X86/X86DisassemblerDecoder.c
+++ b/arch/X86/X86DisassemblerDecoder.c
@@ -2094,6 +2094,7 @@ static bool checkPrefix(struct InternalInstruction *insn)
 			case X86_BTS64mr:
 
 			// CMPXCHG
+			case X86_CMPXCHG16B:
 			case X86_CMPXCHG16rm:
 			case X86_CMPXCHG32rm:
 			case X86_CMPXCHG64rm: