Photo via Tegan and Sara

Montreal's Osheaga Festival was already one to watch this year, but during Macklemore and Ryan Lewis' set on Saturday night, the pair was joined by Canadian sister duo Tegan and Sara for "Same Love," which originally features Mary Lambert on vocals.

After praising Canada for their more "evolved" views on social issues, Macklemore surprisingly introduced the duo, prompting the audience to erupt in excitement. Tegan and Sara were themselves performing at the music and arts festival this weekend, but the Seattle rapper invited them to join him for this particular song, which is special to both parties. Macklemore has been a passionate advocate—a rarity in his genre—for equal rights, something which hits home for Tegan and Sara, both of whom happen to be gay.

The crowd clearly loved the collaboration, cheering with approval during the second verse's lyrics when Macklemore utters, "No freedom 'til we're equal. Damn right, I support it," referring to gay marriage.

Watch the performance below via Warner Bros. Records (updated with official video footage).