Fans in Toronto got a real treat Monday night when John Mayer brought out special guest Shawn Mendes to join him on stage.

The duo performed a mashup of Mendes' smash hit "Mercy" and Mayer's classic, "In Your Atmosphere."

The two preformed an acoustic mix, each singing their own and each other's verses, in a song that Mayer deemed "over the top good" when he shared a photo of the performance on his Instagram Tuesday.

"The dynamite @shawnmendes joined me in Toronto tonight perform a "Mercy"/"In Your Atmosphere" mashup and it was over the top good. #thesearchforeverything #shawnmendes #bringingbacktheworddynamite." Mayer captioned the photo.

Mendes, who has said before that his biggest inspiration and idol is John Mayer, was truly gushing on stage during the whole performance. Mendes later took to his Twitter as well as his Instagram to share the sweet memory with his fans.

"Damn. John Mayer is the best. My job is the best. U guys are the best. What an insane night," he said.

Thank you so much @johnmayer

A post shared by Shawn Mendes (@shawnmendes) on

Watch the performance up top.

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