Matt Damon and Luciana Barroso are one of the most enduring celebrity couples, and it just might be down to an unbroken rule.

The Hollywood star, who stars in Christopher Nolan’s new epic, The Odyssey, has been married to his wife, 49, since December 2005. Since then, the couple has welcomed four daughters, Alexia, 27, Isabella, 20, Gia, 17, and Stella, 15. Damon and Barroso’s secret to a successful marriage? One “non-negotiable” rule they’ve not broken in 20 years.

While promoting The Odyssey, the Good Will Hunting star, who draws the line at one body change, said he and his wife have a family dinner every night. However, the actor admitted that, despite never breaking the rule, he and his family sometimes struggle to stay present with each other. It comes after Damon, 55, revealed his secret to dropping 30 pounds for his role in The Odyssey.

• The View’s Sunny Hostin captured pleading with cops over son’s trespass on cop’s bodycam

• Fox News issues humiliating on-air clarification after Trump’s ‘false’ election claims

“We have family dinner every night, and that’s non-negotiable, and it’s always been that way,” Damon told People, but sometimes the family struggles to connect during those meals.

The star divulged, “One of my daughters said, ‘Well, family dinner, last night we didn’t talk.’ And we realized, ‘Oh my gosh, you’re right.’ We sat down for dinner, and you can get lost in that routine a little bit and not appreciate why you established the routine in the first place.”

Damon, who met Barroso at a Miami bar in 2003, added, “That’s the kind of family mindfulness we’re all working on.” Now, two of the couple’s daughters have left home, while the younger two remain at home.

“I feel like we are facing it and embracing the fact that it’s happening,” the Boston native said about him and his wife becoming empty nesters soon. “We’ve been talking a lot about presence and about really trying to be in the moment, and because you can’t slow time down, the only way to really do it is to really be there and be in it.”

Damon added that he and Barroso are “trying to be mindful of holding onto what we can.”

The star opening up about his family life comes after he revealed earlier this year on SiriusXM’s The Howard Stern Show that Barroso thought his Good Will Hunting co-star Ben Affleck was “the cute one” in the film.

Damon explained, “After we’d been together for a little while, probably a few months, she admitted that – I think I met her best friend from high school, and it came out that the two of them went and saw Good Will Hunting together, and her best friend thought I was the cute one, and she thought Ben was the cute one.”

“So she admitted to me… I’m like, ‘You got the wrong one?’ She told me that 23 years ago,” the star revealed. Damon’s latest role as Odysseus in Christopher Nolan’s new epic, The Odyssey, also involves an enduring marriage.

In the film, which hit theaters on Friday, July 17, Damon’s Odysseus is married to the fiercely loyal Penelope (Anne Hathaway), his queen, who must fend off potential suitors in his absence.

The film has been called Nolan’s “most extreme” to date. It had a $250 million budget, making it the most expensive film of his career and his first film shot entirely on IMAX 70mm cameras.

Meanwhile, Matt Damon said he waited 45 years for the call from Ben Affleck about The Odyssey.