Use `mrb_test` instead of `mrb_obj_eq`;
@@ -408,7 +408,7 @@ os_memsize_of(mrb_state *mrb, mrb_value self)
const mrb_kwargs kwargs = { 1, kw_values, kw_names, 0, NULL };
mrb_get_args(mrb, "o:", &obj, &kwargs);
- recurse = mrb_obj_eq(mrb, kw_values[0], mrb_true_value())? mrb_hash_new(mrb) : mrb_nil_value();
+ recurse = (!mrb_undef_p(kw_values[0]) && mrb_test(kw_values[0]))? mrb_hash_new(mrb) : mrb_nil_value();
total = 0;
os_memsize_of_object(mrb, obj, recurse, &total);
