Selena Gomez fans are in for an extra special treat. The starlet's second UNICEF charity concert is tonight, and rumor has it a certain someone will make a special appearance -- none other than Gomez's boyfriend, Justin Bieber!

AOL Music (via Hollywood Life) reported, "Justin will be a surprise guest at Selena's concert. UNICEF is really important to Selena and Justin knows this."

The concert will be one of the last North American dates for Gomez for a while. The singer-actress announced in December 2011 that she and her band, the Scene, are taking a break from music while she focuses on her film career. The 'Hit the Lights' singer will first embark on a South American tour, for which Bieber may also join her.

"Even though he's in the studio right now working on his album, Justin's going to make time to go down to South America," a source said. "Plus, they love traveling together."

Gomez became the youngest ever UNICEF ambassador in 2009 when she was only 17 years old, and the organization is as close to her heart as the Biebs is. “Giving back has always been important to me,” she said in a statement when her concert was announced. “This concert allows me to connect with my fans in person which is one of the best parts of my job and to raise money for important causes at the same time. I can’t think of anything I would enjoy doing more.”

Well, maybe one thing.