“Oh, that was a real flamethrower.”

Leonardo DiCaprio talked about the tough day on the set of “Once Upon a Time in Hollywood” when he had to use a flamethrower to burn up a pack of brave stuntmen dressed as Nazis. He was joined by co-stars Brad Pitt, Julia Butters, Margaret Qualley and Mike Moh to discuss Quentin Tarantino’s film during the Variety Screening Series presented by Vudu.

“The first day I used that was a really hard day. All the greatest stuntmen in this town’s history showed up for that Nazi convention. It was amazing. I really had to blast them with a real flamethrower and torch all of them,” DiCaprio said.

The initial flamethrower scene was part of Rick Dalton’s (DiCaprio) fictional movie-within-a-movie called “The 14 Fists of McCluskey,” which was also a reference to the fiery ending of Tarantino’s “Inglourious Basterds.” The devastating weapon returned in the dramatic finale of “Once Upon a Time,” as well.

“That heat just wafted right back into my face. I started to get chronic headaches that day. I knew the flamethrower thing was coming back up again, but that was in the opener, thank God,” DiCaprio said.

Pitt, who played Dalton’s stunt double, Cliff Booth, had a laugh when he saw his co-star’s name on the call sheet for that day.

“It said ‘LDC flamethrower rehearsal,’” he said. “I was like, ‘Aww, that’s going to suck. That’s really going to suck.’”