[GAMEPLAY] Backstabing Swashbuckler!

There be a bug in Gankplanks Aresenal! I was playing as Caitlyn and chasing an enemy, Gangplank being on my team ult'd to slow them, and it had no effect, yet, it effected me instead, not sure if this was a one time happen stance, but it could potentially be a huge problem as it's cc alone is terrifying and you don't want to box in your team or be boxed in by a teammate. lol