require validation fail when passing a non-english char.

[eluser]ted wong[/eluser]
Hi all, I have a validation like this:

Code:

$this->form_validation->set_rules('description',
             'lang:post_description',
             'required|min_length[1]|max_length[255]');

When I pass the english ONLY content, it works. But when I pass something like "測試" or "測試ABC",
It just don't work. And told me that : The Description field is required.
Is that true the required field support english ONLY. If yes, I need to write my own call back?
Thank you.