Game allows me to register ineligible players

I'm playing as FC Porto; I'm into my third season. I recently had to register players for the Champions League group stage. As I normally do, I had the computer pick my registered players and then made changes from it's initial recommendations. One of the players it suggested I register was my new signing Kara from Fiorentina. Although I should have realized this at the time, it turns our Kara had played in a Champions League qualifying game for Fiorentina. However, the computer suggested I register him on my team in place of other eligibile players and allowed me to do so. Now, I'm about to play my first CL match and Kara is ineligible. I know he should be ineligible from having played previously for Fiorentina, but certainly I should not have been allowed to register him, let alone have him suggested in my CL squad.

Edit: Turns out it was a Europa League qualifying game. That makes me think that he should be eligible, but either way, something is fishy. He should either be eligible, or be unable to be registered.