Britney Spears recently performed her newest hit song Perfume during her Las Vegas performance. However, the performance didn’t go over well with her fans, who are now accusing her of lip-syncing.

According to the gossip site Oh Not They Didn’t! , Spears is moving her lips to the words, but the audience is only hearing Sia’s version on the song. Sia is best known for her song Chandelier, and was one of the writers of Perfume.

“If you listen closely to the performance video, you can make out some of Spears’ vocals under Sia’s more charactered voice,” Billboard’s Colin Stutz said. “That’s because, most likely, Spears uses Sia’s track as an in-monitor guide when she sings. Only this time it was put into the house mix, making for an embarrassing accident.”

This isn’t the first time that Spears has been accusing of lip-syncing, and her managers have had to come to bat for her over the scandals. “To put on the show that she puts on, it’s virtually impossible to sing the entire time and do what she does. She’s singing on every song, basically, when she has the ability to sing. There’s no way you can dance for 90 minutes straight and sing the entire time,” Adam Leber, Britney’s manager, said.

You be the judge. Check out Britney and Sia’s music videos below: