Can't use smite in enemy jungle (possible glitch?)

So recently (since probably 4.20 or 4.21) there have been many times where it won't let me target monster in my opponents jungle for smite. I have seen it most often with blasting smite, and especially if they are currently attacking that camp. I've had no problems with my own, neutral camps, or minions. Only enemy jungle camps. Also, I'm playing on the mac client.

Has anyone else experienced this?