Damon shared the nugget on ‘LADBible’ while alongside Emily Blunt.

Matt Damon’s opening up about a kissing scene with Scarlett Johansson in their 2011 film We Bought a Zoo, and there’s a perfectly good reason why he described one particular kissing scene as “hell.”

Taking part in LADBible TV‘s “Agree to Disagree” with Emily Blunt, Damon and his Oppenheimer co-star were discussing whether they agree or disagree it’s only right to tell someone they have bad breath. They both agreed that they should — however as subtly as possible — before the topic of bad breath in intimate scenes was brought up by a producer. And that’s when Damon spilled the tea.

“I had to kiss Scarlett [Johansson] — had to kiss. Can you imagine how horrible that was for me? — but we did,” said Damon before Blunt jokingly gave him a hard time about how bad that must have been for him, given Johansson’s soft lips and all.

After laughing it off, Damon explained.

“It was hell, ok? What happened was we did a shot before lunch and it was like this nice little two-shot that ended in the kiss,” he said. “And it was really good. And we went to lunch and she and I both thought it was over. She ate like an onion sandwich for lunch. And she came in and [We Bought a Zoo director] Cameron Crowe had set the camera up and it was like a tight shot of the kiss. And she goes, ‘Oh s**t.’ She goes, ‘I literally just had I had like an onion sandwich. I thought we did this.'”

Damon went on to say that he made fun of Johansson’s breath, though he did ultimately clarify that “her breath smells like roses.”

Damon and Blunt have been doing a lot of press together lately as they continue to push the hugely successful Christopher Nolan-directed drama based on Julius Robert Oppenheimer, the American theoretical physicist and director of the Manhattan Project.

In fact, Damon and Blunt go way back, as he’s friends with her husband, John Krasinski, who apparently gave Damon a hard time for having to pass on James Cameron’s 2009 Avatar. Damon first told ET back in May that turning down the lucrative role of playing Jake Sully (a role that ultimately went to Sam Worthington) was “the dumbest thing an actor ever did in the history of acting.” Had he accepted the lead role, Damon would have earned around $250 million due to a huge backend deal.

While revisiting the story in a CNN interview with Chris Wallace (conducted before the SAG-AFTRA strike), Damon shared Krasinski’s reaction after telling him he turned down the role, due to being contractually tied to the Bourne franchise.

“I told John Krasinski, we were writing this little movie a long time ago called Promised Land and we were in my kitchen and it was a Saturday morning and we were on a break and I tell him about Avatar, and he launches himself out of the chair,” Damon tells Wallace. “He starts pacing the kitchen, he goes, ‘Nothing in your life would be different today if you had done that movie, except you and I would be having this conversation in space.'”