Shaco boxes don't proc spellthief

It is a bug that i thought would be fixed with the shaco update as amny other bugs. I play shaco support a lot and i have to buy ancient coin because spellthief doesn't proc off of the jack in the box. I believe it is not intentional as it procs moby boots (which is quite a shame as I can't buy it when playing ad shaco jungle as I don't know when I will lose my movement speed suddenly.)