Image upload how to force lowercase the file extension??

[eluser]123wesweat[/eluser]
yep, i know that one but i can't get it to work.

tried

Code:

$config['file_name'] = strtolower('avatar_'.$user_id);

and

strtolower($upload_data['file_name']);

does something like this exist

Code:

$config["extension_tolower"] = TRUE;