Control's new Ultimate Edition requires you connect to the internet to play its single-player campaign - but only once, and only for the disc-based version of the game on Xbox.
Eurogamer understands this is because the disc does not actually contain all of the game's campaign data, the remainder of which is then downloaded. There's no suggestion the game needs to connect online for any other purpose.
The issue was highlighted over the weekend on Twitter by DoesItPlay, which stated it had seen reports players can progress as far as the game's opening maintenance elevator without the internet before being instructed to download the update.
Control publisher 505 Games has now commented on the issue, and confirmed it is due to the game's overall size.
"Control Ultimate Edition, including all the latest expansions is over 50GB so we're unable to fit everything on the Xbox disc. We have used Xbox intelligent delivery to provide some content on the disc and the rest via download," the publisher wrote in a statement.
"On PlayStation 4, this isn't the case as Control Ultimate Edition fits on a single disc, due to compression and other variables.
"Once you have downloaded the game, rest assured you do not have to be online to play!"
There's no further mention of why the game was able to fit on a PS4 disc but not an Xbox one.
Control's Ultimate Edition is Remedy's controversial new version of the game with its two expansions included. Buying it now will grant you the game's next-gen visual upgrade for PlayStation 5 and Xbox Series X at some point in the future. The only way to access this upgrade is with the Ultimate Edition, something which upset some fans when it was announced.
Of course, you can still continue to play the original version of Control on next-gen consoles via backwards compatibility - and there's been no word on what the next-gen versions unlocked with the Ultimate Edition will actually add to the game.