The Harry Potter star was promoting her upcoming project in Hollywood in a low-cut, nude-coloured Giorgio Armani gown on Monday night (10Sep12) when the top of dress shifted, giving fans and photographers a peek of her silicone pastie.
The 22 year old failed to notice the slip-up and carried on posing for pictures.
Earlier this month (Sep12) Watson revealed she had hired a stylist in a bid to prevent embarrassing red carpet moments, telling Glamour magazine, "I have to (work with a stylist) at this point... These gowns are ridiculous. You're being photographed from every angle, so not only do you have to consider how the thing looks, but whether you're going to be able to sit in it and whether people are going to be able to see up your skirt."
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