Problem with inheritance

[eluser]masterix[/eluser]
I haven't found it so I post here.

I have following dependence hierarchy in my project:

Code:

class Admin extends Controller
class NewsAdmin extends Admin
class ArtAdmin extends Admin
class ConfigAdmin extends Admin

The problem occurs when I invoke NewsAdmin controller. CI doesn't know anything about Admin class. It can be solved by adding:

Code:

require_once('admin.php');

but this solution isn't nice for me. Is there any other ?

Thanks in advance for help.