Christopher Nolan鈥檚 latest film, 鈥淥ppenheimer,鈥 has become one half of the box office and pop culture phenomenon 鈥淏arbenheimer,鈥 sweeping up glowing reviews along the way.

But eagle-eyed fans have spotted a mistake in a scene set in 1945, as Cillian Murphy鈥檚 J. Robert Oppenheimer stands among a crowd waving American flags 鈥 bearing the wrong number of stars.

鈥淚t was good and all, but I鈥檒l be that guy and complain they used 50-star flags in a scene set in 1945,鈥 Twitter user Andy Craig wrote on Friday.

In 1945, the American flag featured 48 stars, as Alaska and Hawaii hadn鈥檛 yet become U.S. states.

It wasn鈥檛 until July 4, 1960 that a 50-star flag was first flown in the U.S..

But in another scene set in the same year, the correct American flag flies behind Oppenheimer.

One Twitter user had a theory: 鈥淚 can argue that this is done intentionally as the colored scenes were from Oppenheimer鈥檚 perspective, while the black and white scenes were from another. This would be a memory of Oppenheimer from his present day memory which does have 50 states on the flag.鈥

The film depicts the events of Oppenheimer鈥檚 life, flitting between his days as a student in the 1920s, his time overseeing the development of the nuclear bomb during World War II, and the U.S. Atomic Energy Commission committee hearings in 1954 during the McCarthy era, in which he was stripped of his security clearance due to his associations with the Communist Party.

鈥淏arbie called this in didn鈥檛 she,鈥 another Twitter user joked, referencing the fact that 鈥淥ppenheimer鈥檚鈥 release date coincided with Greta Gerwig鈥檚 鈥淏arbie.

Coming in behind 鈥淏arbie,鈥 鈥淥ppenheimer鈥 opened at $80.5 million in the U.S. over the weekend, according to Comscore. Both movies essentially doubled predictions from weeks ago, Paul Dergarabedian, senior media analyst at Comscore, said.

It鈥檚 unprecedented to not only have two films do so well, but also to help each other with the 鈥淏arbenheimer鈥 trend, Dergarabedian said.