The fast food chain is introducing a meat-free version of its flagship Whopper. And no, it’s not an April Fools’ joke, though you could be forgiven for thinking so.

The Impossible Whopper is made in conjunction with Impossible Foods, whose “Impossible Burger” has won raves from even hardcore carnivores for having many of the same qualities as a beef burger, while still being entirely plant-based.

Burger King isn’t the first fast food chain to team with Impossible (Carl’s Jr. and White Castle have both offered Impossible versions of their own burgers), but none have embraced the concept quite so enthusiastically. The Impossible Whopper will be served at 59 Burger King locations in St. Louis initially, but it’s expected to be rolled out to 7,200 stores nationwide soon after.

The partnership between the two companies is an unusual one. Impossible has been dedicated since its inception to promoting plant-based foods. Burger King, meanwhile, almost fetishizes ground beef in its commercials, regularly showing burgers being cooked over an open flame.

The company hasn’t been afraid to shake things up, though. Its 2018 Nightmare Burger came on a green bun and it has publicly trolled both KFC and McDonald’s in the recent past.