diff --git a/gc.c b/gc.c
index c70f8a35a7..fa4ab44712 100644
--- a/gc.c
+++ b/gc.c
@@ -2754,7 +2754,8 @@ rb_data_object_check(VALUE klass)
 {
     if (klass != rb_cObject && (rb_get_alloc_func(klass) == rb_class_allocate_instance)) {
         rb_undef_alloc_func(klass);
-#if 0 /* TODO: enable at the next release */
+#if RUBY_VERSION_SINCE(3, 2)
+        RBIMPL_TODO("enable the warning at this release");
         rb_warn("undefining the allocator of T_DATA class %"PRIsVALUE, klass);
 #endif
     }