Kass and his ult

So is kass supposed to be able to be knocked up out of rift walk? I was playing against a Quinn and I was knocked out of my ult multiple times. I have played a lot of kass and I know when he gets out. When the Quinn would jump on me she was able to knock me out of it sooner than I am used to. Isn't kass supposed to be un-targetable for a very short duration when he enters the void?