Baby Zombie Speed Bug

Hi,

I have Baby Zombie with Speed Path on 4. When I get a kill it's supposed to give me speed 3 for 10s after every kill. The only problem is when I get a kill it's not giving me that.

Proof: Imgur showing my Path lvl: http://imgur.com/zYm2F5i

YouTube: My killing someone with babyzombie. :

Edit: Sorry for the poor quality =(