I'd like the game to boot in windowed mode.

I have an ultra-wide screen and fullscreen does not look good for this game (it stretches a lot and won't adapt to the resolution). There's an option to disable fullscreen, but for some reason every time I exit from the Options menu the game reverts to fullscreen again. Alt+Enter does work once in-game, but the fact that this has to be done at all to get the game windowed is annoying. I would like to know if there's a config file I'm missing somewhere or some way to start the game in windowed.