As Pigeons And Planes reports, the duo’s onstage collaboration took place as Lamar headlined the second night of the Montreal event.
Footage of the team-up (below) shows Lamar Lamar spotting his “big bro” Bey at the side of stage and encouraging him to make an appearance for the huge crowd in attendance.
When Bey eventually takes to the stage, he dances his way through Lamar’s King Kunta, before the crowd start chanting lyrics from Alright.
“This is a real moment for me,” Lamar tells the crowd. “This is somebody that inspired me to do what I do.”
Bey eventually takes the mic and raps on a special version of Alright. Catch fan-shot video of the special moment, below.
Watch: Kendrick Lamar – King Kunta & Alright (ft. Mos Def) @ Osheaga 2015