Justin Bieber surprised Selena Gomez fans with an onstage performance at her concert at Pacific Amphitheatre in Costa Mesa, California on Sunday.
After being announced and coming on stage, Bieber, 17, started his performance by hugging Selena and than sang a bit of his song Favorite Girl, before going on to cover Justin Timberlake's Cry Me a River.
After the concert, Justin tweeted
"U did great tonight. proud of u."
Selena spent her 19th birthday on July 22 with Justin. The two went to Disney World and dined together during the weekend.
In a recent interview with Germany's TV Digital Selena opened up about Bieber, "It's just nice to have someone at my side who understands me.
"I have friends who are in show business and I have friends who are not. Of course it's great to have someone like him, who understands what it means to work in this business."
Selena, however, remains firmly grounded.
"But on the other hand, it's also nice to talk with someone about the real world, a person who knows nothing about photo shoots and all these things,", she added. "I think the secret is to have a balance of both."