No shield Icon on uninterruptible spells

Hey,

I don't know if this is a bug or intended, but neither on icecrown nor on blackrock uninterruptible spells are marked with a shield for my warlocks. I guess that it's because my pet has the interrupt ability and not me, but it's still annoying because I have to check ennemi buff bars before kicking instead of just immediately seeing if I should bother interrupting. I searched for an addon that does this job, but couldn't find one so far. Even steady shot is marked like an interruptible spell for me. Any help or information is appreciated!

Kind Regards!