[Gameplay] No Coin From Poison

So, I'm not sure if anyone reported this, but I assume this is a bug. Anywho, as a support, I took my utility masteries which are supposed to give me a coin every time an ally kills a minion, but when my Teemo ADC (Yes, you heard that right. No, it's not that good.) use his poison to get cs, when the minion died, I wouldn't get the coin, but he would still get that cs. Is this a bug? Is it supposed to be like that?