Class not found

[eluser]gtipete[/eluser]
im trying to do some simple authentication by extending the Controller class. Here is my code.

Code:

<?php
class MY_Auth extends Controller {
    
    function MY_Auth()
    {
        parent::Controller();
        if(!isset($this->session->userdata('logged_in')) || $this->session->userdata('logged_in') != TRUE)
        {
            redirect('user/login/', 'refresh');
            exit;
        }
    }
}
?>

This is called MY_Auth.php and located in the libraries folder. When try to extend this class, i get the following error:

Fatal error: Class 'MY_Auth' not found in C:\xampp\htdocs\gallery\system\application\controllers\gallery.php on line 2