The 28-year-old actress said that back in 2005 her 'Pride and Prejudice' director Joe Wright did not allow her to purse her lips on screen, reported Us magazine.
"I've got it out of my system. I didn't know I did it so much, and Joe banned it from the film," she said.
The Oscar-nominated British actress and Wright went on to work together in 'Atonement' (2007) and 'Anna Karenina' (2012).
But it was only until 2011 that Wright finally relented on the ban when the two teamed up for a Chanel perfume campaign.