diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 202757ba7cf..36db7a18cf3 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -172,7 +172,7 @@ def ptr_rc_nosp : PointerLikeRegClass<1>;
 //
 def X86MemAsmOperand : AsmOperandClass {
   let Name = "Mem";
-  let SuperClass = ImmAsmOperand;
+  let SuperClass = ?;
 }
 class X86MemOperand<string printMethod> : Operand<iPTR> {
   let PrintMethod = printMethod;