Although they have been keeping it secret, Wiz Khalifa's fiancé Amber Rose may have spilled the beans on the their baby's gender. The pregnant model tweeted out a photo on Sunday (Oct. 21) of a gift from a friend and purposely revealed the sex of their unborn child.

The picture features a graphic image of Guns 'N' Roses guitarist Slash on a baby-sized onesie. "My friend Maria bought our Lil Boy this Slash onesie..... Oops did I say Lil Boy??? ;-)," she wrote.

Amber, who is in her second trimester, also celebrated her 29th birthday on Sunday, as well. Her boo Wizzy presented her with a Slash Hat birthday cake, which she also shared with her fans on Twitter.

If you're asking yourself, what's up with all the Slash motifs? Well, Rose's all-time favorite musician is Slash from G'N'R. Rose is so enamored by Slash, she even dressed like him for a Halloween bash in New York City last year.

In an 2011 interview Global Grind, Rose explained her infatuation with the legendary guitarist. "He is one of my favorite people in the world! He has been my hero since I was a little girl; I always looked up to him," she says. "He was a biracial rock star, and anytime he plays the guitar it just takes over my body. His sound is just amazing to me."

"Most of my persona has a lot to do with Slash. I have a very mysterious persona and there are a lot of things that people don’t know about me and Slash is like that," she continues. "He is like that to this day! He is very mysterious and people are just so intrigued by him and he has been out for 20 plus years! He wrote a book and you still want to know more."

Since we now know the sex of their baby, Wiz and Amber should reveal the little Wizbud's name. Slash Khalifa would be a cool baby name -- don't you think?

Listen to Amber Rose Talk About Natural Birth + Wiz Smoking in the House