The "Girlfriend" singer, 39, invited her ex-husband and fellow Canadian rocker Whibley, 44, on stage during her Greatest Hits Tour at the MGM Grand on Saturday night June 1 in Las Vegas to perform Sum 41's hit song "In Too Deep" with her.

On June 1, Lavigne welcomed Whibley on stage during her Greatest Hits Tour at the MGM Grand. She shared a compilation video on her Instagram, showing that she welcomed him to sing the Sum 41 song “In Too Deep” with her.

T he When We Were Young festival isn’t for another four months, but Las Vegas became a pop-punk haven during Avril Lavigne’s concert at the MGM Grand Garden Arena on Saturday, June 1. The “Girlfriend” singer, 39, brought out her ex-husband Deryck Whibley, 44, for a surprise performance of Sum 41’s hit “In Too Deep” as part of the concert.

Avril Lavigne brought out Sum 41 frontman Deryck Whibley to perform 'In Too Deep' in Las Vegas over the weekend. Watch it here.

Avril Lavigne brought her Greatest Hits tour to the MGM Grand Garden Arena in Las Vegas Saturday night, and that’s not all she brought. Deryck Whibley, Lavigne’s ex-husband, was on hand to perform “In Too Deep” from his band Sum 41.