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Justin Bieber reportedly donated $545,000 to AIDS charities at a gala in Cannes on May 22.

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The "Baby" hitmaker attended the amfAR Cinema Against Aids bash at the Cannes Film Festival in France along with other celebrities including event host Sharon Stone, Heidi Klum and Leonardo DiCaprio, who auctioned off a trip into out of space with him at the annual auction.

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Sources tell TMZ that Bieber watched as one guest pledged $545,000 to the charity before quietly announcing that he would match the donation.

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Staff reportedly checked with the singer, who confirmed he was certain he wanted to give the huge amount.

Bieber subsequently took to his Twitter page and wrote, "Amfar #giveback."