diff --git a/vm_core.h b/vm_core.h
index edcfdb7abc..e7104818c0 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -497,7 +497,7 @@ static inline const rb_iseq_t *
 def_iseq_ptr(rb_method_definition_t *def)
 {
 //TODO: re-visit. to check the bug, enable this assertion.
-#if 1 || VM_CHECK_MODE > 0
+#if VM_CHECK_MODE > 0
     if (def->type != VM_METHOD_TYPE_ISEQ) rb_bug("def_iseq_ptr: not iseq (%d)", def->type);
 #endif
     return rb_iseq_check(def->body.iseq.iseqptr);