Yasuo's Wind wall does not work???

So, it was another fun day at summoner's rift, and i was wandering about in the jungle. I manage to steal red buff and killed nocturne at his spot. Their support was coming to kill me, and teemo was behind her. I used my wind wall to make sure teemo's Blinding dart did not hit me; but somehow, his dart went through the wind wall, and killed me. What the heck?! is anyone getting this bug too?