How to upload mp4 files with file grid field

Hi.

I need to upload mp4 files via a file grid field so I followed these [instructions] (https://docs.expressionengine.com/latest/general/system-configuration-overrides.html#mime_whitelist_additions) and added this code to mimes.php

$config['mime_whitelist_additions'] = array(
  'video/mp4'
);

Unfortunately, it doesnt work for me. Maybe I have made a mistake?