Uncharted’s upcoming spinoff, The Lost Legacy, might be over 10 hours long, according to developer Naughty Dog.

In an interview with IBTimes UK, the company’s head of communications, Arne Mayer, said “we couldn’t keep it short.”

“Years ago, when we were asked if we were ever doing a single-player expansion for Uncharted we always said, ‘Well, we don’t have the self-discipline to do that,'” recalled Mayer. “If we tried to do that we’d create a full game.

“There’s no way we could constrict and restrain ourselves, and that’s exactly what was happening here. When we were doing story pitches, we were coming up with a game that would be over ten hours long and so we suddenly realised everything we said was true and we couldn’t keep it short.”

While the final length of The Lost Legacy was not revealed, Mayer’s comments suggest Naughty Dog was not able to shorten the story’s length and it therefore may take some time to complete.

Uncharted: The Lost Legacy stars series favorites Chloe Frazer and Nadine Ross, and it doesn’t feature Nathan Drake at all. It’s an expansion, of sorts, to Uncharted 4: A Thief’s End, though it is standalone, so you don’t need to own Uncharted 4 to play The Lost Legacy. Naughty Dog previously made a standalone expansion to The Last of Us, titled Left Behind, though that originally launched as DLC and only had a runtime of around three hours.

Naughty Dog says The Lost Legacy will contain the Uncharted series’ biggest ever level, though it is likely to be the company’s last-ever game in the franchise.