Fans of the well-known director Christopher Nolan were shocked to find out that he made a big mistake in his hit movie Oppenheimer.

Fans of the historical thriller starring Cillian Murphy and telling the story of J. Robert Oppenheimer and the creation of the atomic bomb went on social media to point out a mistake in the background of the movie.

Some people on social media say that the Oscar-nominated director made a mistake in the scene after the 1945 bombs of Hiroshima and Nagasaki that shows the flag of the United States of America.

After the bombs, Murphy’s character was asked to give a speech, so the scene showed him walking to the stage as the crowd cheered and waved US flags.

A fan noticed that the flag had 50 stars, but the flag of the United States only had 48 stars at the time. “It was good and all, but I’ll be that guy who complains that they used 50-star flags in a scene set in 1945,” the tweet said.

In the movie, the story is told from three different points in time. It shows Oppenheimer’s early life and his work on the A-bomb, switching between scenes from his security hearing in 1954 and Lewis Strauss’ approval hearing in 1959.

But in another scene from the same time period, the “correct period-accurate flags” were used, which has led some fans to think that Nolan didn’t make a mistake after all.

“Personally I think it was done intentionally because colored scenes were from Oppenheimer’s perspective which is his present day’s memory that was after the 50-star flag was established,” one user wrote.