Sherlock fans might want to start bracing themselves for a bittersweet farewell—because if co-creator Mark Gatiss is to be believed, the most recent season may have been the detective series’ last.

Over the weekend at the WhatsOnStage awards, Gatiss hinted at the series’ possible end, largely attributing it to scheduling issues with stars Benedict Cumberbatch and Martin Freeman.

“I honestly don’t know if there will be any more,” Gatiss said, according to The Sun. “It’s incredibly difficult to get Benedict and Martin’s diaries to align. And obviously we left it in a very happy place. . . If that’s the end, I’d be very happy where we left it.”

Gatiss, who also plays Mycroft Holmes on the series, was referring to Season 4’s very definitive closing episode—an installment that several reviewers noted felt a lot like a series finale, down to the very conclusive mini-montage in its final moments.

Disappointed as they may be, Sherlock fans shouldn’t be surprised to learn that the show may be over. As The Hollywood Reporter notes, both of Sherlock’s stars are increasingly tied up in the Marvel universe—Cumberbatch as Doctor Strange, and Freeman as Everett K. Ross in Black Panther—and Cumberbatch also has responsibilities with SunnyMarch, his production company.

And scheduling difficulties may not be the only reason Sherlock could be drawing to an end. The series’s fourth season, though rife as ever with easter eggs, set a record low in overnight ratings with its season finale—though the numbers could also be attributed to a leaked Russian-language version of the season’s closer. (The BBC launched an investigation to determine whether the leak was an accident, or purposeful piracy.) Diehard fans might insist there’s more to mine from this world, but others—including, it seems, at least one of the show’s co-creators—might prefer to embrace the elementary solution of letting this series say a quiet, if bittersweet, goodbye.