get base_url() inside custom config file

[eluser]ibnclaudius[/eluser]
How can I get base_url() inside custom config file?

This:

Code:

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

$config['css'] = '' . base_url() . '/static/css';

Output this:

Code:

Fatal error: Call to undefined function base_url() in /var/www/_meuboletim/application/config/meuboletim.php on line 3