The SexyBack singer co-hosted a disco-themed party to celebrate the film about Bogart, who founded Casablanca Records and was closely aligned with the rise of disco.
Justin - who was joined at the event by his wife Jessica Biel - took to the stage and teased guests by singing a few lines from songs including Last Dance, Ain't No Sunshine and Donna Summer's Love To Love You Baby.
Bogart is said to have convinced Donna to record a second version of the song - in which she simulates the sound of a woman in the throws of ecstasy - as long as 20 minutes.
Justin joked that the long version allowed women enough time to satisfy themselves.
He added: "But we're in Cannes, so I don't need to tell you about partying."
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