By Olivia Bahou
Updated Aug 04, 2016 @ 11:00 am
Credit: Craig Barritt/Getty

Hilary Duff’s 4-year-old son is a big boy now! The pop star revealed that her adorable son Luca Cruz is already a big fan of ghost stories in the sweetest bedtime Instagram.

In the pic, Duff props herself up on her elbow while in bed with her adorable tow-headed son. Wearing a scalloped bandeau bikini top, minimal makeup, and a loose updo, the singer looks positively frightened at Luca’s open-mouthed roar. “Ghost stories…..” she captioned the sweet snap.

This isn’t the only look at Duff’s cute son we’ve gotten this week: The 4-year-old also proved that he has the Ghostbusters theme song (almost) down pat. “Who you gonna call? I mean, I mean. ... Something strange in the neighborhood. Who you gonna call? Ghostbusters!” he says in this hilarious video.

“Guys! I don’t love to put my kid on blast but this is just too good! #ivewatchedit200times #thiswillbeshownathiswedding #ghostbusters #whoyagunnacall #lucanailedit,” she captioned the post.

We can’t get enough of this mother-son duo.