Something new for Fallout is coming, apparently. It remains to be seen exactly what it is, but now we pretty much know it’s not coming from Fallout: New Vegas studio Obsidian.

In a tweet today, the California-based studio said, “How do you let someone down easily? Asking for a friend.” The tweet used the ultra-sad hashtag #ItsNotUs. The Obsidian tweet never mentions Fallout by name, but it’s clear what its talking about.

Obsidian developed the much-loved Fallout: New Vegas, which was released in 2010 for PlayStation 3, Xbox 360, and PC. Last year, that game’s director, Josh Sawyer, said he and other Obsidian developers want to make another Fallout game someday.

Before that, Obsidian CEO Feargus Urquhart talked about his potential plans for New Vegas 2. “I think if we were to do Fallout: New Vegas 2–or just a new Fallout–we would probably separate it from what the internal team at Bethesda’s doing,” Urquhart said back in 2013. “We’d keep it on the West Coast, because we’re West Coast people. They’re East Coast, so it makes sense.”

The latest Fallout game was Fallout 4, which was developed by Bethesda Game Studios in Maryland, came out in November 2015; it sold really well.

Obsidian’s latest game is Pillars of Eternity II: Deadfire, which was released earlier this month on PC. The studio is also working on an unannounced RPG that will be published by Red Dead Redemption parent company Take-Two’s new indie game label.

As for Bethesda’s latest Fallout tease, it’s not clear what it’s for or when we will find out more. Bethesda’s E3 2018 press conference is set for Sunday, June 10, at 6:30 PM PT / 9:30 PM ET (2:30 AM BST / 11:30 AM AET on June 11), so we should find out more then at the very latest. For more, check out the full E3 2018 press conference schedule.

Back in February, Bethesda’s Todd Howard said the studio had multiple “big and crazy” projects in the works across its network of studios, including the studio it opened in Montreal. One possibility for the Fallout reveal is a new mobile game, as Bethesda already said it plans to make more mobile titles in the future after Fallout Shelter‘s huge success. Additionally, Howard has talked about how he has “lots of ideas” for what might come next after Fallout 4.