(Gameplay) Knock Up does not stop Katarina's Ult

Just played a bad game as Riven and noticed that Katarina Continues to Ult while mid air from knock up. I know that a Knock up is an interrupt and It may be that she doesn't stop ulting till she hits the ground but the would defeat the purpose as she can still do a ridiculous amount of damage within that second she is in mid air. This needs to be looked into but ill try testing this in custom games with other knock ups to see if it is just Riven's.