David Corenswet watches his language as Superman. In James Gunn’s new film, the star generally portrays the classic comic book character with an “Aw, shucks” sort of attitude. Clark Kent may lose his temper, but the Man of Steel wouldn’t dare curse in public.

Corenswet, on the other hand, incidentally let an expletive fly on set.

The actor was featured in a two-person interview for People alongside Lois Lane actress Rachel Brosnahan. In the video, the pair was asked, “What’s the most surprising thing your co-star did while filming?”

Corenswet recalled an on-camera moment where Brosnahan caught him so off guard that he cursed her out.

“She made me curse at her,” Corenswet said.

“Well …” Brosnahan laughed.

“The way she delivered one particular line made me sort of involuntarily say, ‘Oh, f–k you!’” Corenswet went on. “Which I think was a shock to all of us. She got me. She caught me off guard and made me feel really hurt in that moment, and so I — in character — shot back at her.”

You can watch the full clip below:

Neither Corenswet nor Brosnahan mentioned which scene the f-bomb dropped during, but it seems likely to have happened during the filming of an interview between Lois and Superman. In the scene, which was featured in the film’s first official trailer, the romantic couple sits down for a one-on-one interview between the Daily Planet reporter and the Last Son of Krypton. Things quickly turn heated as Lois presses Superman on questions about his attempt to quell an international invasion. The Man of Steel bends more than once, losing his cool at the line of questioning.

It’s an electric moment between the two new “Superman” stars. Not only does the interview highlight Lois’ journalistic prowess, but it also highlights Superman’s frustration as he settles into his role as a world protector early in his career.

“I give her great credit,” Corenswet said. “It’s not easy to surprise your scene partner.”

“It was fun to watch him work,” Brosnahan continued. “He’s a really fearless actor. I think he was playing with the different sides of this character all the time.”

This isn’t the only time expletives flew on the set of “Superman.” In a recent interview with GQ, Corenswet and Gunn noted that he would sometimes curse at his star’s persistent line of acting questions.

“Sometimes his questions are great, and I totally see where they make him better, and because they make him better, they make the movie better,” Gunn told GQ in an interview out Monday. “But every once in a while, it’s just one question too many, and it’s like, ‘Oh, my God, just, David, stop, stop, for a minute.’ And the beautiful thing about me and David is that he knows that about himself and he knows where my limits are. And when I say, ‘David, shut the f–k up,’ David totally gets it and does not take that personally.”

“After we finished shooting, we were hanging out and [James] affectionately — I think — described me,” Corenswet said. “He said a very nice thing: ‘You’re a filmmaker, and so you want to be involved in the filmmaking and you want to help make the film as good as possible.’ Then he said, ‘I think you’re also like a kid sticking his finger in light sockets and sometimes I gotta slap you on the wrist and say stop f–king doing that.’”