Demi Lovato and boyfriend Wilmer Valderrama celebrated their six-year anniversary Sunday.

The 23-year-old actress marked the occasion by sharing a cuddled-up selfie with the 35-year-old actor and a timeline of snapshots from each year of their relationship on Instagram.

Lovato and Valderrama have been together since 2010, but told E! News there's "no rush" to marry. The couple mourned their dog Spawn's death in December, just five months after their pet Buddy was killed in a "tragic accident."

"I met him five years ago and we became close after that," the singer said of Valderrama in September. "I looked at him and was like, extremely attracted to him. Who isn't? When I first met him, I'm not shy [about] dating older men, and he was like, 'You're too young. [But I'm] not anymore."

Lovato credited Valderrama with helping her keep healthy when she celebrated her third year of sobriety in March. The singer thanked her beau for "supporting her recovery," saying she "really wouldn't be alive today without him."

"I wish I could put into words how grateful I am for this man right here," she wrote. "But my love has grown to a level that words could never possibly express how much this man completes me."

Lovato released her fifth studio album, "Confident," in October, and guest starred on Valderrama's El Rey series "From Dusk Till Dawn" the same month. The actor plays Carlos Madrigal on the horror-drama, which will return for a third season this year.