Robert Downey and Susan Downey Robert Downey and Susan Downey

Robert Downey Jr. has spilled the beans: He and wife Susan are having a baby boy.

The Iron Man star revealed the sex of his impending child, who is due in February, Monday night on The Tonight Show with Jay Leno. "I am not permitted to discuss it," he joked. "I can't say a word... We're having a boy!"

Robert Downey Jr., wife expecting baby

This is the second child for Downey, who has a 17-year-old son, Indio, with his ex-wife, Deborah Falconer. However, this is the first child for he and wife Susan, who have been married for six years. "I don't want to be presumptuous," he told Jay Leno, "But I think actually it's been tougher on me. Just the hormones and the mood stuff and the nausea and the whole thing."

"I gotta be careful," Downey quickly added. "I am going to have to see my wife some time after doing this segment with you, and I think I'm already in trouble."

Check out Downey's appearance to find out the gift Leno gave him: