Fans spot historical mistake in ‘Oppenheimer’ involving a flag

Christopher Nolan’s summer blockbuster “Oppenheimer” is surely not bombing at the box office, but there is one scene in the movie that isn’t hitting the right target.

One moment in the three-hour film starring Cillian Murphy shows a historical error that viewers pointed out on Twitter.

In the shot, the Irish actor, 47, stands in the middle of a crowd, who all clap and cheer for him while they wave American flags.

The dramatic epic about the life of nuclear physicist J. Robert Oppenheimer takes place in the early 1940s, but the flags featured white stars that represent 50 states — despite the country only having 48 in 1945 when the scene took place.

Hawaii and Alaska, the last two entities to be annexed to the United States, were not added until 1959.

Eagle-eyed fan Andy Craig revealed the mistake on social media, sharing a snapshot of the scene, and his post quickly went viral.

“It was good and all, but I’ll be that guy and complain they used 50-star flags in a scene set in 1945,” he tweeted.

Other fans agreed with his discovery and even called out Nolan, 52, for the incorrect usage.

“Totally ruined the film for me,” a person claimed. “Yeah, but that’s not Nolan…so he had to have just missed it. He is ‘mostly’ British, afterall,” one joked about the “Batman Begins” director’s nationality.

Someone else chimed in: “That’s an amazing ‘catch.’ Now I’ll never ‘not’ see it.”

“Also the flags seem poorly printed… there’s no padding between the bottom row of stars and the boundary of the canton,” a user noted.

Another fan scoffed: “It seems sloppy: they put substantial effort into everything else, but the 48-star flag was official from 1912 to 1959, it was the only US flag of the period.”

Some also explained that the 48-star flag was even used in other scenes in the film.

“Shocked Nolan made that mistake. Dude will probably reshoot for the disc release before he digitally changes it,” a moviegoer said.

“Oppenheimer” has a stacked cast, including Matt Damon, Robert Downey Jr., Florence Pugh, Emily Blunt, Rami Malek and many more.

It chronicles the man growing into his moniker of the “Father of the Atomic Bomb” and his efforts with the Manhattan Project during World War II.

According to Blunt, 40, Murphy achieved the look of Oppenheimer — who was gaunt and thin — by scarcely consuming food.

“He had such a monumental undertaking,” she told Extra earlier this month. “And he could only eat, like, an almond every day. He was so emaciated.”

The “Peaky Blinders” alum also discussed his weight loss for the role in a May interview with the New York Times.

“I love acting with my body, and Oppenheimer had a very distinct physicality and silhouette, which I wanted to get right,” he said. “I had to lose quite a bit of weight, and we worked with the costume and tailoring; he was very slim, almost emaciated, existed on martinis and cigarettes.”