Harrison Ford is sharing one of the surprising secrets behind his 15-year marriage to wife Calista Flockhart.

During a recent appearance on NPR’s Wild Card with Rachel Martin, the 83-year-old actor opened up to Martin about what age has taught him about love. “Old people can love, too,” he said.

“You know, you think about falling in love and all of that business,” Ford continued. “You think it’s the business of youth or something, you know, and staying in love is the issue. Maintaining, nurturing, basically, not f—— up.”

After Martin noted that couples in relationships “work on that every day,” the Shrinking star added he allows himself a little leeway. “With some days off for bad behavior,” he quipped.

When asked how long he and Flockhart, 60, have been married, Ford replied, “If you ask me, I would say all my life. I was married for the first time at 23 years of age, which should be illegal.”

The star wed his first wife, Mary Marquardt, in 1964 before splitting in 1979, and was also previously married to screenwriter Melissa Mathison from 1983 until their divorce was finalized in 2004. He tied the knot with Flockhart in 2010.

Ford and Flockhart, who celebrated their 15th wedding anniversary in June, began dating after meeting at the 59th Golden Globe Awards in 2002. The following year, the Indiana Jones star declared, “I’m in love,” in an interview with Hello! magazine.

“Romantic love is one of the most exciting and fulfilling kinds of love, and I think there is a potential for it at any stage of your life,” he added to the outlet. “I was not surprised that I was able to fall in love, and I wasn’t surprised that I did.”

Ford proposed to Flockhart over Valentine’s Day weekend during a family vacation in 2009, and the couple got married in New Mexico the following year. Ford adopted Flockhart’s son, Liam, whom she welcomed via adoption in 2001.

In a 2008 interview with Reader’s Digest, Ford praised Flockhart’s dedication to motherhood and opened up about the joy of having Liam, now 22, in his life.

“She’s a mother by choice — she adopted Liam before we met, as a single parent, which is an awesome responsibility to take. She’s devoted herself to Liam and has done a really wonderful job raising him. I’m happy to now have a part of the job,” he said.

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“She’s brought a child back into my home,” Ford continued. “My youngest, other than Liam, is 17. It’s a wonderful opportunity to be part of a child’s growing up, which is always an endless springtime. You see the blossoming and the growing and the nurturing and the payoff.”

The 1923 star is also dad to sons Benjamin, 58, and Willard, 56, whom he shares with Marquardt, along with son Malcolm, 37, and daughter Georgia, 35, whom he welcomed with Mathison.