On September 24, 2012, the Sex Pistols will celebrate the 35th anniversary of their album Never Mind the Bollocks, Here’s the Sex Pistols with a box set reissue. One of the previously unheard bonus tracks is a “lost” demo of the controversial, Holocaust-themed “Belsen Was a Gas,” recorded in 1977 by Johnny Rotten, Sid Vicious, Steve Jones, and Paul Cook.

Thought to be written by Sid Vicious, the song originally appeared on The Great Rock ‘n’ Roll Swindle. You can stream it below. (via Slicing Up Eyeballs)