The Stranger Than Fiction star and Viveca Paulin already have a son, Magnus, 2

Will Ferrell, who announced in July that he’s expecting his second child with wife Viveca Paulson, has revealed the baby will be a boy.

Appearing on The Late Show with David Letterman Monday night to promote his new movie Stranger Than Fiction, Ferrell, 39, was asked if he knew the sex of the upcoming arrival.

“You know, I don’t know if I do,” he said. “I’ve gotta check my Blackberry.”

Looking uncomfortable, he continued, “Well, we do know, but I forget if we’re telling people. I told the Today show we weren’t telling them. But it’s a boy.

Ferrell and Paulson, 37, an art auctioneer, already have one son, Magnus, 2.

Asked by Letterman how Magnus is handling the idea that he’ll have a new brother come late December, Ferrell said, “He doesn’t like it. He’s in denial about it. … I’m like, ‘You better live it up now, cause No. 2 is coming and it’s not going to be fun for you.’ “