"I am not permitted to discuss it," he at first told Jay Leno Monday when the Tonight Show host asked if the actor knew the sex of his child yet. "I keep dropping the ball everywhere. She'll say don't tell your cousins until...and then I tell 'em."
"I can't say a word...we're having a boy!"
And if mom-to-be Susan Downey wasn't thrilled at that spat-out proclamation, she'll be doubly unexcited by his next revelation.
When asked by Leno if he was feeling any sympathy pains for his pregnant wife, he went one better.
"I don't want to be presumptuous, but I think it's been tougher on me. Just the hormones and the mood stuff, and the nausea, the whole thing," he laughed. "I gotta be careful. I am going to have to see my wife sometime after doing this segment. I'm gonna be in trouble."
Here's hoping he can smooth things over by late February, which is when his missus is due.
As it goes, it'll be the first child for Susan, but baby will make two for RDJ, who already has an 18-year-old son, Indio. Congrats!