Firmware of the body wasn't the latest, but updating it didn't help. The lens firmware was already up to date.
It's weird - basically, the lens behaves like it's been set to auto, so I'm not able to expose manually.
SOLVED: Just figured it out, I'm stupid. Since the lens in question doesn't have an aperture ring, the F value changes either through the dial that's set up to control the aperture or when you zoom in and out. So, I've accidentally set it to auto without realizing. The few other lenses I've tested with all had aperture rings, so it wasn't obvious to me immediately what's going on.
elgatoloco got a reaction from mrPeter in Exposure indicator