[GAMEPLAY] Sion stunning himself after landing ult. ON PLAYERS

I played a game as Sion and I am almost positive I was self stunning very often when landing a knock up on a player. I noticed the stun icon once and the other times I couldn't Q because I was stunned. Can anyone else back me up on this? I am almost positive I was stunning myself when landing ults on players and not getting stunned from other forms of CC.