wplang_ not found by wp-config.php

Hi there,

I am following the instructions to enable more languages to a site. I get stuck at this point

9. To enable languages on your site:

Open your wp-config.php file in a text editor and search for:
define ('WPLANG', ' ');
Edit this line according to the .mo file you’ve just downloaded, e.g. for the Portuguese spoken in Brazil you must add:
define ('WPLANG', 'pt_BR');

What I need to do if I find no wplang at my config.php?

Is this just a question of including a line like this or is it not needed anymore with the new WP version (4.1)?

Thanks for your help!