--- a/js/src/jit/IonAnalysis.cpp
+++ b/js/src/jit/IonAnalysis.cpp
@@ -2556,17 +2556,18 @@ TryOptimizeLoadObjectOrNull(MDefinition*
             break;
           case MDefinition::Op_StoreSlot:
             break;
           case MDefinition::Op_ToObjectOrNull:
             if (!eliminateList.append(ndef->toToObjectOrNull()))
                 return false;
             break;
           case MDefinition::Op_Unbox:
-            MOZ_ASSERT(ndef->type() == MIRType_Object);
+            if (ndef->type() != MIRType_Object)
+                return true;
             break;
           case MDefinition::Op_TypeBarrier:
             // For now, only handle type barriers which are not consumed
             // anywhere and only test that the value is null.
             if (ndef->hasUses() || ndef->resultTypeSet()->getKnownMIRType() != MIRType_Null)
                 return true;
             break;
           default: