Holly Madison and Pasquale Rotella attend the Electric Daisy Carnival on June 8, 2012 in Las Vegas, Nevada. Credit: Jeff R. Bottari/WireImage.com

Looks like the cat's out of the bag -- and it's a girl!

Holly Madison's boyfriend, Pasquale Rotella, appeared to let it slip on Twitter this past Tuesday, Oct. 16, that their baby-to-be is a girl.

"Off to Amsterdam and I already miss my girls," the Electric Daisy Carnival founder tweeted, along with a photo of Madison and a sonogram of their baby.

"We are very excited!" he added later, responding to a follower's congratulations on his "little fairy tale princess."

It seems Rotella, 38, missed the memo that Madison, 32, was keeping the gender of their unborn child under wraps.

"We’re not telling anybody yet, but we found out and I'm really excited!" the pregnant Peepshow dancer told Us earlier this month. "I'm really excited about decorating the nursery, so we've already started buying some things there."

Madison broke the news of her pregnancy exclusively to Us Weekly in August, saying she had "always wanted to be a mom." She has neither confirmed nor denied Rotella's tweet, but either way, she still has at least one secret yet to be revealed.

"I don't want to say what the names are, but I will say that they're very unusual," the former Playboy Playmate and Girls Next Door star teased, adding that her tastes run close to Gwyneth Paltrow's. "Kind of Apple-ish, along those lines. I don't like common names at all. If I've heard it before on somebody more than one time, it's out!"