Mexico’s historic Chapultepec Castle has been seen flying the black Targaryen flag, and officials in Mexico aren’t amused.

The plot of the “House of the Dragon,” a “Game of Thrones” prequel, apparently involves countries around the world taking sides in a civil war for control of the Iron Throne.

The producers of the HBO series posted a video Monday of the 19th-century Mexico City hilltop castle showing the black Targaryen flag hanging over the battlements. The flag, representing queen Rhaenyra, predictably has a dragon on it.

Mexican officials issued a statement Monday saying it wasn’t true, and threatening to sue. But it’s not because they support Laenor Velaryon.

Mexico’s National Institute of Anthropology and History said the flags had been generated by some sort of technology, and had never really hung at the site.

The institute, which is the legal guardian of the country’s historic buildings and artifacts, was hopping mad that the historical site had been used in the ad campaign, and said they would take legal action.

“The reproduction of images of this site for use in promoting this series has not been authorized,” said the statement by the institute, known as the INAH. “For this reason, the INAH legal department will take all necessary legal measures, because this constitutes an improper use of images of a historical site.”

HBO did not immediately respond to messages seeking comment.

It is unclear whether Mexico can win the legal battle against artificial intelligence and computer-generated images. The institute did not claim authorship rights of the original video. The site is open to the public, so anyone could have filmed it.

During the 1846-48 Mexican-American War, the castle was the site of the 1847 battle of Chapultepec, when Mexicans defending the heights where the castle stands died rather than surrender to U.S. troops.