diff --git a/py/emitnative.c b/py/emitnative.c
index ad8f04aac7..3bc637ac63 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -1737,8 +1737,13 @@ STATIC void emit_native_for_iter(emit_t *emit, mp_uint_t label) {
     emit_get_stack_pointer_to_reg_for_pop(emit, REG_ARG_1, MP_OBJ_ITER_BUF_NSLOTS);
     adjust_stack(emit, MP_OBJ_ITER_BUF_NSLOTS);
     emit_call(emit, MP_F_NATIVE_ITERNEXT);
+    #ifdef NDEBUG
+    MP_STATIC_ASSERT(MP_OBJ_STOP_ITERATION == 0);
+    ASM_JUMP_IF_REG_ZERO(emit->as, REG_RET, label);
+    #else
     ASM_MOV_REG_IMM(emit->as, REG_TEMP1, (mp_uint_t)MP_OBJ_STOP_ITERATION);
     ASM_JUMP_IF_REG_EQ(emit->as, REG_RET, REG_TEMP1, label);
+    #endif
     emit_post_push_reg(emit, VTYPE_PYOBJ, REG_RET);
 }