Fans in attendance at Olivia Rodrigo’s Toronto concert at Massey Hall on Friday night received more than they bargained for when Avril Lavigne made a surprise appearance onstage to join the “Drivers License” singer.

Wearing a red plaid skirt, black leather jacket and big, bulky boots, Lavigne and Rodrigo delighted the crowd with an enthusiastic duet on Lavigne’s 2002 hit “Complicated”.

READ MORE: Olivia Rodrigo Kicks Off ‘Sour’ Tour And Rocks Cover Performance Of Avril Lavigne’s ‘Complicated’Β 

“Jumped up to sing ‘Complicated’ on stage with @oliviarodrigo in Toronto tonight,” wrote Lavigne on Instagram, sharing photos and video of the pair singing together in front of the rapturous audience.

“It was very sweet to perform with you tonight on your SOUR tour!!” Lavigne added. “Have an incredible tour gurl. Keep killing it. Sending you so much love.πŸ§‘πŸ’€πŸ’œ”

Rodrigo has been regularly performing “Complicated” throughout her Sour tour, but this marks the first time that she and Lavigne have sang it together.

ET Canada was on hand for the show, sharing video of the duet on Twitter.

Check out more fan-shot footage below.

@jessbosnjak

NO WAY DID THIS JUST HAPPEN #oliviarodrigo #sourtour #avrillavigne #fyp

♬ original sound – jess

@virginradiotoronto

@livbedumb brought out avril lavigne!!!

♬ original sound – VirginRadioToronto

@thisisvalley

Reply to @shekindaeats #oliviarodrigo #sourtour #avrillavigne #part2

♬ original sound – VALLEY