Microsoft first announced support for cross-platform play at E3 last year, but Sony has been hesitant to enable it. Eurogamer reports that Reddit users have noticed that Epic’s co-op survival game, Fortnite, has been quietly updated to support cross-platform play between Xbox One and PS4 players. An Epic Games spokesperson confirmed to the The Verge that this was an unintended mistake. “We had a configuration issue and it has now been corrected.”

Earlier this year, Sony refused to enable cross-platform play for both Rocket League and Minecraft, despite Microsoft and Nintendo both supporting it across Xbox One, PC, and Switch. Rocket League developer Psyonix previously said the game would support PS4 cross-platform play in “less than an hour all over the world” if Sony removed its blocks.

Sony hasn’t shown an interest in enabling this key feature, and disabling it simply encourages friend groups to buy a PS4 if they want to play with their friends. Microsoft has been pushing cross-platform play at a time when it’s struggling to compete with Sony’s strong PS4 sales. The glitch demonstrates just how easy it is for PS4 players to play against Xbox gamers.

Update September 18th, 2:25PM ET: This article has been updated to reflect Epic Games’ official statement on the glitch.