Undead Labs’ zombie-survival game State of Decay has been granted an R18+ adult rating by the Classification Board, receiving approval to be sold in Australia.

Aussie gamers are to receive a special edition of State of Decay.

The game was previously refused classification on the grounds that it contained “illicit or proscribed drug use related to incentives or rewards".

The original State of Decay submission included in-game medications that consisted of both legal and illicit substances. A special edition was re-submitted for classification, which developer Undead Labs described in a post on its Facebook page with, “Stimulants out! 'Supplements' in!"

The special edition of the game has been rated for mild impact drug use and sex, high-impact violence, and moderate impact language and themes. No further details regarding an Australian release date have been revealed.

State of Decay focuses on surviving in a zombie-infested world, and promises a dynamically generated experience. It will be released exclusively for the Xbox 360, although developer Undead Labs has made reference to a PC release in future.

The game sold over 500,000 copies on the Xbox Live Arcade within three weeks of its release in North America, making it the fastest-selling original game on XBLA.