What’s the biggest no-no topping when it comes to pizza? If you said pineapple, you’d be wrong.

Turns out, there’s one even grosser.

Papa’s Tomato Pies in Trenton, New Jersey, created a concoction, which swaps out traditional tomato sauce for yellow mustard.

According to co-owner Francis Garcia, the pizza came about after a drunk patron tried ordering a mushroom pie and was mistakenly heard as “mustard pie.” While some are claiming the unusual pizza is a hit, many aren’t so enthused. One Twitter user even went so far as to say, “This should be illegal.”