Borderlands maker Gearbox Software has trademarked the name Z-Day.
The filing was spotted by Siliconera, but no one's any wiser about what the name's for.
A new game? Perhaps. A new Borderlands expansion? Maybe. Something to do with zombies? Probably.
We do know that Gearbox is a busy studio. As well as Aliens: Colonial Marines, Gearbox claims to have three other secret games in development.