Upload class won't upload .ico

I'm trying to upload .ico files using the upload class, however, it returns 'The filetype you are attempting to upload is not allowed.' as the error.

I have updated the mimes.php file array with the following:

PHP Code:

'ico'   =>  array('image/ico', 'image/x-icon', 'application/ico', 'application/x-ico', 'application/x-win-bitmap', 'image/x-win-bitmap', 'application/octet-stream'), 


Here is my current code:

PHP Code:

$config['upload_path'] = 'files/';
$config['allowed_types'] = 'ico';
$config['max_size'] = '2000';
$config['max_width'] = '0';
$config['max_height'] = '0';
$this->load->library('upload', $config);
if ($this->upload->do_upload('icon'))
{
 die('ok');
}
else
{
 die($this->upload->display_errors());
} 


Any help is appreciated. Thank you.