Rockstar's Wild West epic Red Dead Redemption was available via Xbox One for a few hours over the weekend.
Xbox One owners were able to briefly download and play the game if they owned its Xbox 360 version as a digital download.
Red Dead has yet to be announced for Xbox One's backwards compatibility service but has been one of the most-requested games on Microsoft's official Xbox Feedback website since back-compat was announced.
The one weird trick used to get the game has now been shut down, but it involved finding a friend who had selected to 'follow' the game. From their profile, you could then access the game's Xbox One store page and set the game downloading.
Red Dead wasn't the only game to be affected - fans also managed to nab back compatible versions of Alan Wake's American Nightmare, Castlevania: Symphony of the Night, Left 4 Dead 2, Halo Wars, and Tekken Tag Tournament 2.
"All 360 games are tested through an emulator for quality," Microsoft mouthpiece Larry "Major Nelson" Hryb explained via Twitter last night. "Due to an error, games in test were temp available. Apologies."
No need to apologise, Major!
Users report a bit of slowdown in the emulated version of Red Dead Redemption - but this is likely an issue which will be eradicated through further testing.
Microsoft usually announces its regular update of back-compat games towards the end of each month. We'll keep our ear to the ground until then.