A Brooklyn location of the fast food chain Burger King has been advertising that it sells the meat-free Impossible Whopper on Seamless — but instead sends customers regular old beef Whoppers without telling them. At least one vegetarian customer didn’t realize until after he’d already eaten two Whoppers, simply believing the ads boasting the two burgers taste the same.

For at least the last few weeks, the 736 Broadway franchise of the burger chain featured the Impossible Whopper — “100% WHOPPER, 0% Beef” — on its menu, at one point listing it as its most popular item. But serving the burger here is actually impossible, since it’s only available in select cities. A 35-year-old Williamsburg resident, who asked to go unnamed to shield his eating habits, says he only found out when he went into the actual store at a later point to order the burger and was told they don’t sell it.

“I was incredulous,” he says. “It’s maybe 20 percent poisoning. This is a city where there are a lot of reasons why people don’t eat [meat], from religion to health to ethics.”

A manager at the Burger King tells Eater that when a customer orders it, they’ve been sending a classic beef Whopper in its place, asking the driver to inform people of the swap. But drivers have not told multiple customers who ordered the Impossible Whopper that it actually contained real meat, the customers tell Eater. The receipt on the bag also says “Impossible Whopper,” which led the Williamsburg man to believe it truly did contain the trendy plant product.

The restaurant’s Seamless page removed the Impossible Whopper some time on Tuesday afternoon, after Eater sent an inquiry to Burger King corporate and to Grubhub, the Seamless parent company. A Burger King spokesperson chalked it up to a “technology error” from a franchisee.

Other NYC locations of Burger King on Seamless did not list the Impossible Whopper; Burger King, Grubhub, and the franchise would not clarify how only one location had the error.

“We apologize for any confusion this has caused. Any guests who ordered an Impossible Whopper through delivery in the New York area and have any questions may call 1-866-394-2493,” the Burger King statement says.

It’s not known how many people ordered the Impossible Whopper; Burger King did not say. The item — which was listed at the top of the restaurant’s page — had been up since at least May 20.

The Williamsburg customer had eaten Impossible product before at a different restaurant and thought it tasted “80 percent” like a true beef burger; when he tried the Whoppers, he thought the same thing.

“Nope,” he says. “The Whopper is just shittier than I remember.”