Zend Framework Class Inheritance - Modules with Prefix

I'm developing a PHP project with Zend Framework and I have the following problem:

I created a class called BaseController in my module "Admin". I seted the option:

resources.frontController.prefixDefaultModule = "true"

So the names of my controllers are "Admin_IndexController", "Admin_UsuarioController", and so on.

I need "Admin_IndexController" extends "Admin_BaseController" (a class also created by me) however, I get only the message that the class was not found.

Note: I have already tried to rename the class to "Admin_BaseController" or just "BaseController" or implement in "Admin_IndexController" the code

class Admin_IndexController extends Admin_BaseController 

or

class Admin_IndexController extends Basecontroller

and no option solved the problem.

Does anyone have any idea what it could be?