May 21 (UPI) -- Elle Fanning says her dress is to blame for her "fainting spell" in Cannes.
The 21-year-old actress posted Monday on Instagram about fainting during a dinner party at the Cannes Film Festival.
Fanning shared a photo of herself giving a thumbs up for the camera. She explained in the caption her vintage dress was too tight around the waist.
"Oops, had a fainting spell tonight in my 1950s Prada prom dress but it's all good!! #dresstootight #timeofthemonth," the star wrote.
Former Mad Men stars January Jones and Kiernan Shipka were among those to comment on the post.
"Where's your smelling salts when you need em??" Jones wrote.
"you're a literal icon," Shipka added.
Variety said Fanning, a Cannes jury member, fainted during the Chopard Trophée dinner Monday. Fanning collapsed and fell off her chair during the ceremony, leading to a brief pause in events.
Sources told E! News Fanning "quickly recovered" before leaving the room.
"Most people in the room didn't even notice until after there was a brief pause, during which word quickly spread through the venue about what happened," an insider said.
Fanning is known for the films Maleficent, The Neon Demon and The Beguiled. She will reprise Aurora in Maleficent: Mistress of Evil, which opens in theaters in October.