WATCH: Shawn Mendes Does 'Carpool Karaoke'

Shawn Mendes has revealed he would pay up to $500 for a pair of Justin Bieber’s used underwear.

“I’d buy them,” the singer told James Corden in the latest instalment of Carpool Karaoke. But, he insisted Bieber's briefs would have to be sweaty. “I want to know what he did … the pair of underpants he played hockey in. Otherwise it’s pointless to me.”

In addition to belting out his hits “There’s Nothing Holding Me Back,” “Mercy," "Lost in Japan" and “In My Blood” while driving around Los Angeles, Mendes also talked about his passion for Harry Potter.

MORE: Shawn Mendes Reveals He Loves Booze (And Bieber)

The 19-year-old told Corden about living on his own in Toronto, spoke of his native country (“it’s great there”) and challenged him to a hockey shoot-off.

Mendes is appearing all week on The Late Late Show with James Corden. On Monday's episode, he performed "Nervous."

Watch the fun go down: