It happens to the best of 'em.

Charli XCX made her debut as one of Taylor Swift's Reputation Tour openers Tuesday night (May 8). Unfortunately, so did part of her chest, which was momentarily exposed when a strap on her pink vinyl bralette snapped during her performance.

The Pop 2 singer's "boob fell out," as she wrote on her Instagram Story, during her first song at the University of Phoenix Stadium in Arizona.

After the malfunction, which happened while the pop artist was dancing to her 2014 Billboard U.S. Top 40 No. 1 hit "Boom Clap," Charli apologized to fans on the social media app. "Omg my boob fell out song 1 can u even believe it!!!!! I think I saved it but I’m so so sorry if I flashed anyone I really didn’t mean to I promise," she wrote.

Charli, who was followed by fellow opener Camila Cabello, also performed her songs "Boys," "Break the Rules," "I Love It" (which she wrote for Icona Pop), "Unlock It," "Fancy," as well as a new song called "5 in the Morning."

Later, she joined Cabello and Swift for the pop star's performance of "Shake It Off."

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