Bard Q Vs. Kat Ulti.

So I'm not 100% sure, but I'm pretty darn sure I came across this playing with Bard against a Katarina a few games ago. Whenever Katarina would gank, she would pop her ulti, then in response I would catch her with my Q into a minion, wall, or something. I would see the animation showing she is "stunned", but her ultimate would still continue. Would anyone be able to verify? If so, I'm pretty sure that's not supposed to happen...