Shawn Mendes and A$AP Rocky headlined the Forbes Under 30 Musical Festival in Philadelphia on Tuesday and hung out backstage singing a song together.

Mendes shared this clip on Instagram, which features A$AP Rocky singing, “Look at what I bought, Dior is the coat, you know what it cost.” as Shawn Mendes plays guitar and chimes in with his own vocals.

Forbes, which obviously hosted the event, has the full “performance,” and says “what really happened” when the two met:

Mendes and Rocky both came to the hotel for a photo shoot prior to the show. And before the flashbulbs went off, Mendes was roaming the hall with his guitar, plucking and singing just for fun. At one point, Mendes sat down on the floor near where he and Rocky were both scheduled to be photographed.

When the fashion-forward rapper walked in, decked out in a knee-length black Dior coat, the two struck up a conversation. Soon Mendes was strumming chords and exhorting a bashful Rocky to sing along with him.

Here are a couple more Instagram posts from Shawn Mendes from Tuesday:

Shawn Mendes will appear on the iHeartRadio Jingle Ball tour this December. Check his site for dates. A$AP Rocky has dates spanning the rest of the month and well into November.