It's been almost a year-and-a-half since she's had a real baby bump, but Jennifer Garner is revisiting her pregnant days for her upcoming film.

On Monday (July 29), the "13 Going on 30" actress was spotted on the Los Angeles set of "Imagine," where she wore a large fake belly under a maxi dress.

The upcoming dramedy is officially described as follows: "An old letter written to him by John Lennon and Yoko Ono inspires an aging musician to live life differently, and he sets out to reconnect with his biological son."

The Dan Fogelman-written and -directed flick also stars Al Pacino and Annette Bening, and is set to hit theaters nationwide in 2014.