(CBS News) — A self-described vegan has sued Burger King for allegedly misleading consumers by not informing consumers that its Impossible Whoppers are flame-broiled with the help of beef fat.

Phillip Williams of Georgia, who is seeking class-action status for his lawsuit on behalf of “similarly situated individuals,” said the fast-food company cooks its vegan patties on the same grills as its traditional burgers, thus “covering the outside of the Impossible Whopper’s meat-free patties with meat by-product.”

The meatless Impossible Whoppers are made without beef, but they’re not necessarily vegan-friendly at Burger King locations. On its website, Burger King said the burgers include mayonnaise, which contain eggs. The fast food company also suggests its vegan customers specify that their Impossible Whoppers be cooked separately from the same broilers used to prepare beef and chicken products.

“For guests looking for a meat-free option, a non-broiler method of preparation is available upon request,” reads a footnote for the Impossible Whopper on the Burger King website.

But Williams said he observed, “no signage” disclosing that fact at the Atlanta drive-thru where he recently purchased his Impossible Whopper, a situation he called “deceptive” in his lawsuit. The vegan plaintiff said he believed the burger he ordered sans mayonnaise was “meat free,” but instead felt “duped” by Burger King.

He’s not the only consumer. Customers have taken to social media for months to gripe about the cooking method. Said one Twitter user: “What is the point of the impossible whopper if the patty is cooked on the same broiler as the beef patties? And I wonder how many ppl know.”

A Burger King spokesperson said, “We do not comment on pending litigation.”

Burger King’s parent company, Restaurant Brands International, has said the Impossible Whopper has been a “huge hit” and has helped the fast food chain attract new types of customers. In September, Burger King posted $457 million in revenue for its third quarter, a near 10% jump from the same period in the previous year.

RBI CEO José Cil also said that the Impossible Whopper drove 5% of comparable sales for Burger King last quarter, the brand’s strongest jump since 2015.