When McDonald’s sent an Edmonton restaurant owner a legal order to stop using the name “Effing Filet O’Fish,” he didn’t get mad. He got creative.

Woodshed Burgers owner and chef Paul Shufelt changed the name of his sandwich to “McEffing Fish Filet,” and trademarked it. He says in the last two days it has become the restaurant’s second most popular item—which is pretty unusual for a burger place.

The battle with McDonald’s started on Wednesday, when a cease and desist letter from a law firm representing the global corporate giant popped up in Shufelt’s inbox.

It ordered Woodshed Burgers to immediately stop using the name “Effing Filet O’Fish”—which has been on the menu since opening day on July 2—on social media, its website, menus, clothing, and signs. Basically, everywhere.

The email explained, “McDonald’s is concerned that your restaurant’s use of Effing Filet O’Fish, particularly in association with a sandwich or burger menu item, is likely to cause confusion among consumers and is also likely to diminish and dilute the strength of McDonald’s trademark.”

Shufelt didn’t let the letter faze him. “If anybody walked into our little restaurant and thought they were in a McDonald’s, they might want to get their eyes checked,” he said. “It’s laughable and flattering at the same time. We took it in stride, but we’re also not going to roll over and lie down.”

Shufelt says he trademarked the new name, McEffing Fish Filet, later that same day.

“Our restaurant is so tiny that we just have a chalkboard on the wall and we literally erased the chalkboard and updated our website. Within three hours it was done,” he said.

McDonald’s Canada told VICE via email that: "McDonald’s takes intellectual property rights very seriously. Canadian trademark law requires a trademark owner to take steps to prevent the unauthorized use of its trademarks, regardless of who is using them, or risk losing the rights to those trademarks."

There are 37,855 McDonald’s restaurants globally, employing more than 210,000 people as of 2018. It is the world’s largest restaurant chain based on revenue.

Woodshed Burgers is a single, independently owned restaurant that Shufelt opened this summer. It seats a maximum of 49 people. It grinds its burgers daily, bakes buns from scratch, and makes all condiments in-house.

Other Woodshed Burgers menu items pay homage to other fast-food places, including the “Crispy Colonel” chicken sandwich.