Paper Villager unlocked 9th trade. (Gold for Emerald)

While was trading with my perfect paper villager, the paper trade stopped working. I looked in his trades and there were 9 of them, the last one being the gold trade. Basicly what I'm saying is a white villager had 9 trade slots. As far as my knowledge goes, they can only have 8. Is this a bug or is this possible in the code?