Jessica Simpson lets slip she's having a boy

While Jessica Simpson wouldn't tell Ellen DeGeneres the sex of her unborn baby, the star slipped on Jimmy Kimmel's show Wednesday night.

In talking about how sick she's been during this pregnancy, Simpson blurted out: "I never knew that a wiener could actually make me nauseous."

Said a surprised Kimmel, "Wait a minute..."

"Well, I guess I just told the whole world I'm having a boy!" said Simpson, whose "Fashion Star" show premieres Friday on NBC.

"Oh! OK, I didn't even know what was happening." replied Kimmel.

Said Simpson, "I'm sweating now."

He tried to see if she would name the baby Ace. But she didn't address that. She was still reeling from the slip-up. "That was totally unplanned."