Mariah Carey is simply too much of a 'true diva' to allow yet another wardrobe malfunction to ruin her day.

The 42-year-old songstress slipped into a sexy black Tom Ford dress for her appearance on American Idol Thursday.

She tweeted a picture of herself in the confection, which featured a plunging sheer panel neckline.

'this Tom Ford dress made of patent leather and black sheer fabric that covers the top (sic),' Mariah captioned the photo of herself perfectly preened for the show.

Moments later her look was ruined.

Stepping on the red carpet ahead of her appearance, Mariah explained to Extra's Terri Seymour she had suffered a mishap.

'Somebody stepped on the back of the dress on the way here so I changed into a Monique Lhuillier moment,' Mariah said of her more conservative black dress.

The singer didn't seem fussed, however.

'Darling, you must be prepared if you're a true diva. If not, whatever!' she laughed with a flick of the hand.

The wardrobe malfunction marked Mariah's second in as many weeks.

Last week a strapless dress she wore to So So Def's 20th Anniversary Concert slipped so low hawk-eyed fans caught a glimpse of her nipple.

Mariah is hosting her first season of American Idol.

She joins fellow new judges Nicki Minaj and Keith Urban, and AI veteran Randy Jackson on the panel of hit US singing competition.

She can certainly afford a few new dresses. In addition to her multi-million dollar earnings as a musician, her salary for one season of American Idol clocks in at a reported $18 million.