diff --git a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
index a842a91bbb069..91edc1a81c3f5 100644
--- a/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
+++ b/llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
@@ -3471,7 +3471,7 @@ bool X86AsmParser::MatchAndEmitATTInstruction(SMLoc IDLoc, unsigned &Opcode,
 
   for (unsigned I = 0, E = array_lengthof(Match); I != E; ++I) {
     Tmp.back() = Suffixes[I];
-    if (MemOp)
+    if (MemOp && HasVectorReg)
       MemOp->Mem.Size = MemSize[I];
     Match[I] = Match_MnemonicFail;
     if (MemOp || !HasVectorReg) {
diff --git a/llvm/test/MC/X86/x86-64.s b/llvm/test/MC/X86/x86-64.s
index a1c7e431cef7e..1b73aced06c7e 100644
--- a/llvm/test/MC/X86/x86-64.s
+++ b/llvm/test/MC/X86/x86-64.s
@@ -869,6 +869,9 @@ movsx (%rax), %ax
 // CHECK: encoding: [0x66,0x0f,0xb6,0x00]
 movzx (%rax), %ax
 
+// CHECK: movzbq	1280(%rbx,%r11), %r12
+// CHECK: encoding: [0x4e,0x0f,0xb6,0xa4,0x1b,0x00,0x05,0x00,0x00]
+movzb 1280(%rbx, %r11), %r12
 
 // rdar://7873482
 // CHECK: [0x65,0x8b,0x04,0x25,0x7c,0x00,0x00,0x00]