Mordekaiser gameplay bug

Whenever you are playing Mordekaiser and use Ravenous Hydra's active and try to attack someone with his Q (Mace of spades) Ravenous Hydra's passive sometimes doesn't work (Its about 50/50, sometime it works sometimes it just doesn't) I played few games and just noticed that sometimes it doesn't work.

1. Get near a minion wave (Or just a random camp)
2. Make sure you have ravenous hydra
3. Use you'r Ravenous Hydra and than your Q (Mace of spades)
4. Auto attack minions (try few times becouse sometimes it just works normally) P.S. It might work just with tiamat, havent tried yet.