Gameplay: Kassadin Passive

So I was playing Kassadin on SR. This was my 13th game in a row playing him and I noticed that his passive is not working. From the video in the champion description and the actually description given, he should be passing through minions (ignores unit collision). However, when I am walking with minions or am with a large group of minions, I collide with them just like any other champion. His early game is really hard without this passive so it needs to be fixed. Just try walking through minions, it won't work.