diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 59c09359bd..f0ab11e536 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1158,7 +1158,7 @@ LInstruction* LChunkBuilder::DoInstanceOf(HInstanceOf* instr) {
 LInstruction* LChunkBuilder::DoInstanceOfKnownGlobal(
     HInstanceOfKnownGlobal* instr) {
   LInstanceOfKnownGlobal* result =
-      new LInstanceOfKnownGlobal(UseRegisterAtStart(instr->value()));
+      new LInstanceOfKnownGlobal(UseFixed(instr->value(), rax));
   return MarkAsCall(DefineFixed(result, rax), instr);
 }