Hilary Duff and Luca in West Hollywood on Feb 22, 2013. Credit: PGpg78/RAMEY PHOTO

Baby Luca is growing up so fast! Hilary Duff announced on Twitter Thursday, Feb. 28 that her 11-month-old son is walking.

"Well I officially have a walking baby on my hands!" the proud mom, 25, wrote. "It's hilarious . . . the wobble makes it look like he's 3 drinks in!"

Duff and her husband, retired NHL player Mike Comrie, are currently enjoying a vacation with their baby boy in Maui, Hawaii. 

"Spoiled baby napping by the pool," Duff tweeted Thursday with a photo of Luca's stroller covered by a blanket.

The former Disney star has been letting loose on her tropical getaway. That same day she shared a photo of herself looking carefree, drinking from a pineapple. She simply captioned the shot, "Happening . . ."

Duff and Comrie have been married for a little over two years, and a source tells Us Weekly "they're closer than ever."

"They make time for each other," the pal says. "Her family babysits so they can go on dates."