[GAMEPLAY] Fizz's ult still stays on me when I use Quicksilver Sash

I was playing a game vs Fizz, I bought a Quicksilver sash just to get the fizz ult off of me, but when i actually use Quicksilver Sash it stayed on me instead of dropping on to the ground. After that I intentionally get ulted again by Fizz and used Quicksilver Sash it was still on me, everyone saw it in that game. I hope this is a bug, because I don't remember Riot changed anything with it.