Can't Cure Zombie Villagers, potion effects

I was recently trying to cure a zombie villager I found, and upon splashing it with the the weakness potion, I couldn't give him the golden apple, nor did it appear he even received the effect. I was next to him and didn't get any effect either. I tried again with another potion, same dealio. I thought maybe something had changed and used a lingering potion, nothing changed. Nobody or anything got an effect and I now have a zombie villager in my house holding a stone...