The `Resident Evil: Afterlife` actress - who is due to give birth to her first child later this year - and her husband Hayes MacArthur have reportedly told pals they found out the sex of their unborn tot, despite initially planning to surprise themselves.
A source told In Touch Weekly magazine: "It`s a boy. At first, they wanted to be surprised, but they just couldn`t help themselves. They`re thrilled!"
The couple can`t contain their excitement and have started decorating a nursery in blue and white in anticipation of the new addition to their family.
The source added: "She is so excited about shopping for the new baby - she has been going overboard buying everything. Although she is only in the beginning stages of putting together the nursery, Ali definitely wants to keep everything eco-friendly and simple."
The 34-year-old star is said to be particularly enthusiastic about shopping in high street stores Target and Baby Gap.
The source said: "She couldn`t believe how much baby stuff they carried!"
Ali recently admitted she loves being pregnant because she can eat what she wants.
She said: "I eat everything. I bake myself strawberry shortcakes and then I wake up at three in the morning and I eat them.
"I love it because so much of the time, I have to be careful.
"I work out. I play certain roles where it`s important for me to look a certain way. But now it`s just freedom. It`s like, `Bring on the Sprinkles cupcakes, pizza, pasta.` I`m loving it!"