Justin Timberlake gave Jessica Biel "custom-designed” ring

Justin Timberlake proposed to Jessica Biel with a “custom-designed” ring.

According to People magazine, the singer popped the question while the couple was in Big Sky Country, on their annual vacation to Montana.

“There was plenty of P.D.A., and they seemed happy,” an onlooker said.

Timberlake, who turns 31 later this month, and Biel, 29, celebrated the happy news with friends.

Last year, the couple spent time apart for several months after being together for four years, since May. They made their split official in March 2011.

By the following September, the two were back on and publicly affectionate together again.