Fans attending Paul McCartney's second weekend at Desert Trip were treated to a surprise appearance by Rihanna, who joined the former Beatle on stage to perform "FourFive Seconds."

The song was written in collaboration with Kanye West and has been performed live frequently by both McCartney and Rihanna since its debut in January 2015.

However, this is the first time the pair have belted out the tune together since the 2015 Grammy Awards.

Rihanna hugged McCartney before exiting the stage.

McCartney then quipped that "we finally found someone under the age of 50," poking fun at the demographic that Desert Trip has attracted.

Neil Young also joined McCartney onstage to perform a mash up of "A Day In The Life" and "Give Peace A Chance."