Credit: Albert Michael/

Mad Men's Jon Hamm isn't ready to make an honest woman out of Jennifer Westfeldt, his girlfriend of 13 years.

Though recent reports claimed the actor, 39, was secretly engaged to the former 24 star, Hamm cleared things up when caught up with him at Charlize Theron's Africa Outreach Benefit in NYC Monday.

"That rumor comes up every six months or so it seems," Hamm told Us. "But if you hear anything different, you let me know."

So what's the hold-up? According to the actor, being in a successful longterm relationship isn't always easy.

"Like anything else, you pay attention to it and work hard at it," he explained.

Perhaps the actor has good reason to be cautious about settling down: he previously told Parade that both he and Westfeldt, 40, grew up in divorced households.

"I don't have the marriage chip," he said. "Jen is the love of my life, and we've already been together four times longer than my parents were married."