The Sometimes hitmaker, who has been playing her Piece of Me residency at the Planet Hollywood resort since 2013, was performing her 1999 hit (You Drive Me) Crazy when she took a spill.

A fan video posted on YouTube.com on Wednesday (29Apr15) shows the star falling over and struggling to get back up.

She later took to Twitter.com after the performance to assure fans she came away unscathed, writing, "Thank you for all of the sweet wishes! Had a little scare on stage tonight with my ankle but I'm ok!"