Can't use corpses as non death knight?

Hey there, I noticed that when I played as another class (I was a shaman) in the tavern brawl and I discovered cards from my opponent (who was a death knight), I was unable to use the corpse mechanics which required me to have dead minions. Now I made sure that I did in fact have a dead minion already, but I was unable to use any mechanics involving corpses. I think that is a problem, since classes/decks that rely on stealing or copying cards from the opponent will be unable to really use a lot of the death knight cards because of this.
I also do believe that this is very inconsistent, since I am able to use the outcast effect even if I am not a demon hunter, and I am also able to overload myself even if I am not a shaman, am able to use combo cards as a non-rogue etc…
So I should therefore be able to use corpses if I use death knight cards, even if I am not a death knight.

Please fix, thx