I actually didn't try to let it autodetect... until now.
~/cursedfs% sudo mount cursed.img mountpoint/
mount: /home/kuba/cursedfs/mountpoint: more filesystems detected on /dev/loop0; use -t <type> or wipefs(8).
Props to whoever thought to check for the case of fricking polyglot filesystem images, though. Probably intended for something boring like corruption, but still, nice.