Ben Affleck recently revealed working with Blake Lively on 'The Town' was quite the ego-deflating experience.

In an interview with Details magazine, Affleck said that as he was in Boston filming the movie, he often drove around with co-stars like Lively to show them his hometown. And during one such jaunt with the 25-year-old newlywed, he discovered their 15-year age gap was even greater than he'd realized.

"I was with Blake, and I saw Matt’s childhood home," he explained. "And I said, 'Oh yeah, that’s where Matt grew up.' And she said, 'Who?' And I said, 'Matt Damon.' And she said, 'Oh my God! You know Jason Bourne?!'"

That probably makes Lively sound like an incredible ditz (and maybe she is because come on), but doing some quick math reveals she was only 10 when Damon and Affleck shot to stardom by winning Oscars for co-writing 'Good Will Hunting' in 1997.

"She really didn’t know," he said wryly. "And I thought, 'There it is. The first age of people who are adults who missed the whole Matt-and-Ben propaganda campaign!' Mostly, it just made me feel old."

Aw. It's okay, Ben. Forty in the new 20. And besides, you always have Jennifer Garner and your millions to keep you young.