Justin Bieber surprises his superfan

Pop star Justin Bieber surprised a superfan, Lynsey Mickolas, 10 years after serenading her with the song "One less lonely girl" on stage.

It was back in 2010 that the two met during a concert.

The singer surprised Mickolas once more during a special moment in the finale on his YouTube docuseries "Seasons", reports dailymail.co.uk.

While Mickolas recalled her unforgettable Bieber moment, the singer prepped for another special performance.

Mickolas, now a forensic chemist living in Virginia, spoke about her August 31, 2010 night at Madison Square Garden.

Years after, it seemed unreal for the fan who told cameras: "To be honest, I don't remember everything from that night because everything just happened so quickly and it was so overwhelming."

"Allison (Bieber's manager) just brings me backstage. She was like, 'You're going to be his 'One less lonely girl' and I was like, 'What?'"

All the while, Bieber is preparing to meet her again.

Despite being used to the spotlight, the singer told cameras: "I'm nervous. I don't know. It's, like, the opposite thing to do. Like, why am I nervous? … She has no idea I'm here."

Then he interrupted her interview.

The fan was sharing her opinion on Bieber's last album "Purpose".

Creeping up behind his fan, the singer said: "Honestly, the 'Purpose' album was really good. But, like, 'One less lonely girl' is definitely up there."

"Did you say, 'Once a Belieber, always a Belieber?'" he went on while a shocked Mickolas turned around to agree.

The pair hugged before a backstage clip from 2010 rolled.