J.K. Rowling wrote a fairy tale for children on her 50th birthday party dress

“Harry Potter” creator J.K. Rowling has written another fairy tale for young readers — but only people with access to her closet might ever get to read it.

In an interview with CNN, the bestselling author told Christiane Amanpour that she penned a story for young readers on a party dress, where it might remain in perpetuity.

“I read that you were considering writing a political book for children, young people?” Amanpour asked Rowling in an interview scheduled to be broadcast Monday.

“Oh, that was a fairy tale,” Rowling responded. “It wasn’t political in a sort of party political sense. I don’t know whether I’ll ever publish that.”

“I will tell you this,” she continued. “The theme of my 50th birthday, which I held at Halloween, even though that’s not really my birthday, was ‘Come as your own private nightmare.’ And I went as a lost manuscript. And I wrote over a dress most of that book. So that book, I don’t know whether it will ever be published, but it’s actually hanging in a wardrobe currently.”

Rowling, who turned 50 in 2015, is in the midst of celebrating the 20th anniversary of the publication of “Harry Potter and the Philosopher’s Stone,” the first novel in her popular series about the English boy wizard with his trademark lightning bolt scar.

The final book in the series, “Harry Potter and the Deathly Hallows,” was released 10 years ago. Since then, she’s published several supplementary books, some print and some electronic, about Harry and Hogwarts, the wizarding school he attends.

She has also written novels for adults. Her series of mystery novels, published under the pen name Robert Galbraith and featuring the detective Cormoran Strike, kicked off in 2013 with “The Cuckoo’s Calling.” In March, she announced the title of the fourth book in the series, “Lethal White,” though no publication date has been set for the novel.