If you've seen any of John Mellencamp's recent round of talk-show interviews for his new musical collaboration with writer Stephen King, 'Ghost Brothers of Darkland County,' you probably noticed the rocker was sporting a black eye. In fact, it was kinda hard to miss.

And while most of the hosts pretty much ignored Mellencamp's shiner during the interviews, David Letterman asked him straight-up about it when he and King dropped by 'Late Show With David Letterman' to promote their work. And Mellencamp admitted he got the black eye from his son.

His 18-year-old son.

As you can see in the above clip, Letterman joked with Mellencamp: "Was there trouble backstage?" And the singer and songwriter replied, after a few seconds of silence, "My son and I had words, and he got a punch in and I didn't." He then added, "He's 6'2" and weighs almost 200 pounds."

Letterman asked why Mellencamp was picking on his kid. The 'Hurt So Good' singer said his own father asked him the same thing. "My son punches me, and my dad calls me and says, 'John, you need to change your attitude,'" he said.

'Ghost Brothers of Darkland County,' which premiered in Atlanta last year, is about a pair of brothers, a girl and some supernatural happenings. Mellancamp and King based their musical on a true story. A soundtrack -- featuring Mellencamp, Elvis Costello, Sheryl Crow and others -- was recently released. The play will hit the road later this year.

Watch John Mellencamp Explain His Black Eye