Sandra Bullock shows off bra in backless dress

Sandra Bullock wore a back-baring Victoria Beckham gown to the London premiere of "The Heat," deliberately showing off her black bra underneath.

Sandra Bullock has developed a reputation as a classy, elegant red carpet dresser, so it was something of a surprise to see her outfit in London Thursday.

Attending the premiere of "The Heat," her new crime-solving caper with co-star Melissa McCarthy, Bullock wore a backless black Victoria Beckham gown.

But, possibly concerned with the loose fit of the dress, Bullock opted not to go bra-free, wearing a black double-strapped bra that she made no effort to hide.

She paired the dress with a black leather belt and black and silver cage heels.

"The Heat" stars Bullock as FBI Special Agent Sarah Ashburn and McCarthy as Detective Shannon Mullins, two lone-wolf law enforcement officers forced to work together to take down a Russian mobster.

The film premieres June 17 and hits theaters June 28.