Katharine R changed?

So I have played Katarina since season two, and what I've always loved is a champion is hiding in a bush next to you where you don't have vision, or someone is invisible right next to you, you can still ult and your ult will light up showing you can use it. But just a couple days ago I played a game with her, and if I lost vision of someone walking into a bush next to me it wouldn't let me ult until I a ward down and it actually cost me that play. I'm not saying its something to rely on or something you will run into a lot, but I just never saw any patch notes saying they changed that.