It does not work. Countless times I've been screwed over by fetter ward not working.

"Time to escape, better cast Fetter Ward and sprint away!" *uses fetter ward and sprint* 3 seconds later I get stunned, heavied and zerged to death.

Last match I used Fetter Ward to safely chase a battle high summoner. Guess what? 2 seconds later a dragoon stuns me and LBs me. To top it off the summoners then kills me while i'm stunned and gets fever. The shame...

Fix it or change the description to "may prevent...".

I get it if there is some animation delay on a sleep cast, but those stuns are instant. And I don't buy that I have a 3 second latency. Well... In most cases anyway.