Custom ENVIRONMENT name

Hi.

I'm trying to use a custom ENVIRONMENT name like 'potato'

but when I define this name

index.php > 

PHP Code:

define('ENVIRONMENT', 'potato'); 


I create the folder 'potato' on the config folder

application > config > potato > config.php

And I get this message "The application environment is not set correctly."

If I change to 'testing' or 'development' it works ok.

It's not allowed to create custom development names?

Thanks.