The United States Department of Agriculture (USDA) removed the fictional country of Wakanda from an online list of nations that have free trade agreements with the United States on Thursday.

There was no immediate response from the USDA for comment. A spokesman told The Washington Post that the inclusion of the mythical African nation from the universe of Marvel superheroes was a mistake made as part of a test officials were running.

Francis Tseng, a New York-based software engineer who was looking for data on U.S. agricultural tariffs for a fellowship he is pursuing, first noticed the listing for Wakanda on the U.S. tariff list and called it out on Twitter.

"I was very confused at first and thought I misremembered the country from the movie and got it confused with something else," Tseng told Reuters.

Before it was removed, Tseng managed to download an Excel sheet listing "Harmonized Schedule" tariff codes for various categories of goods traded between Wakanda and the U.S. including live animals, dairy goods, tobacco and alcohol.

After the list was corrected, Tseng tweeted: "Well, the USDA took Wakanda off the list. Guess we're in a trade war with them too."

The Kingdom of Wakanda is the home of Black Panther, the Marvel superhero, and is portrayed in comic books and the 2018 blockbuster as an isolated African nation with the most powerful technology on the planet.

There was no USDA entry for vibranium, the fictional metal from space that is the source of Wakanda's power. Marvel is owned by Walt Disney Co.