Please make sure you don't already have the DLC, as it'll show up regardless.

Point of warning, while humblebundle didn't say, I just want to caution you that if you live in one of the following countries, you MAY not be able to activate it, as the main game that I am giving away as well are region restricted to exclude those countries. It's probably fine, but just a heads up in case things don't go according to plan.

The countries where the main game couldn't be given away were:

AM, AZ, BY, GE, KG, KZ, MD, RU, TJ, TM, UA, UZ