Weird happenings

So I gave serana Ahzidals ring of necromancy thinking that would be a good combo. She raises a shitty mob but hey it'll do 50 frost damage when it dies. The only thing is, her zombies don't explode but when she kills an enemy they take off into the sky like a rocket. Now granted it's entertaining but not the outcome I was looking for. Does anyone know of a way to fix this?