Supernatural and The Walking Dead star Jeffrey Dean Morgan accidentally let slip that he and his wife, One Tree Hill star Hilarie Burton, are expecting a baby girl, a bit of information he was supposed to keep secret.

Onstage at a Supernatural fan convention in New Jersey on Sunday, Morgan was asked a question about his and Burton's impending baby, which they confirmed last week. In his answer, he let it slip that they're having a girl.

A fan caught the moment Morgan realized his mistake, which Morgan shared on Instagram.

"Whoever took this picture?? Caught a moment... thank you. We shall cherish.... " he wrote. "I texted @hilarieburton right after I spilled the little girl beans... and, as usual... she was a rockstar. After all these years she's come to expect me to be a dope... thank god she gets it, and loves me regardless. Thank you New Jersey, and the incredible @cw_supernatural family!"

The baby will be Burton and Morgan's second child. They have a 7-year-old son, Augustus.

Morgan can be seen on Season 8 of The Walking Dead, which premieres Sunday, Oct. 22 on AMC, or at his farm in Rhinebeck, New York, a little town where he and Burton own a candy store called Samuel's Sweet Shop.