Jessica Biel was caught napping in the car on the way to Justin Timberlake's birthday celebration on Wednesday night (30Jan19).

The SexyBack hitmaker turned 38 on Thursday (31Jan19), but because of his work schedule, he decided to celebrate his birthday the evening before with a night out in New York with his wife.

However, the party got off to a slow start as Jessica fell asleep while they were being driven to their destination.

Justin revealed Jessica's nap session by taking a video of her snoozing on Instagram on Wednesday night besides the caption, "Gotta work tomorrow for my bday (birthday) so wifey really going all out tonight..."

In the video, Justin quietly sings "Happy Birthday to me" to the camera before panning it around to show The Sinner actress catching a nap, with her head tilted back against the car's headrest and her eyes closed. Eventually, Justin's singing gets louder and she turns to look at him and smiles as she says, "I'm just preparing for our big night out... Just preparing."

The 36-year-old justified her nap in the comments under the video, writing, "A girl needs her beauty sleep before you HIT THE CLUB."

Their celebrity pals seemed to enjoy the video, with Josh Brolin simply writing "Hahahahahaha," Rita Ora adding, "Its a absolute vibe (sic)," and Timbaland posting, "Wake uppppppppppppppp (sic)."

The couple, who share three-year-old son Silas, were in the Big Apple ahead of Justin's birthday show at Madison Square Garden on Thursday. The gig was originally scheduled to take place in October (18) but had to be postponed while the singer was recovering from bruised vocal cords.

He has rescheduled all the shows originally set for October, November, and December, meaning his The Man of the Woods Tour will now conclude in April.