Brad Pitt was the epitome of cool and commanding as tough-as-nails stuntman Cliff Booth in 2019’s Once Upon a Time in Hollywood.

But when on set, Quentin Tarantino made it clear who was calling the shots.

According to a People interview, co-star Bruce Dern gave at Cannes, the Oscar winners had a tense exchange while working on the blockbuster film.

In the movie, Dern plays blind ranch owner George Spahn. During one scene, Pitt’s Booth wakes up Spahn to check and see if he’s OK. Dern says he improvised a line.

“When Brad Pitt wakes me up in Once Upon a Time in Hollywood, I’m in the bed and I get up and I’m a little groggy and stuff and I just say, ‘I’m not really sure what’s going on,'” Dern said. “I’m looking at him. [Pitt] cut the camera. He cut the camera.” (Meaning, Pitt told the camera crew to stop recording).

Continued Dern: “The look on Quentin’s face — I mean, he was insanely grave — and he said, ‘Brad, what did you just do?'”

“[Pitt] said, ‘Well, I cut the camera.’ [Tarantino] said, ‘Never again in your life will you ever cut a camera or you’ll be dead in this business. That’s my domain. Don’t stop behavior.’ So then we went on and did the scene and all Brad did was say to him, ‘Well, that wasn’t in the script what he said.'”

The team went on filming, and Dern improvised a different line, “I don’t know who you are, but you touched me today. You came to visit me, now I gotta go back to sleep.”

Dern was at Cannes to premiere director Mike Mendez’s documentary Dernsie.

Representatives for Tarantino and Pitt had no immediate comment.

Dern and Pitt had worked with Tarantino before. Dern previously worked with Tarantino in 2012’s Django Unchained and 2015’s The Hateful Eight, while Pitt worked with the director on 2009’s Inglourious Basterds (in addition, Pitt had a small role in 1993’s underrated True Romance, which was written by Tarantino and directed by Tony Scott).

Pitt will reprise his Cliff Booth character in Netflix’s as-yet-untitled spin-off to Once Upon a Time, which is written by Tarantino and directed by David Fincher. The film will receive a two-week exclusive engagement in Imax starting Nov. 25.