Lupita Nyong’o personally wrote to Taylor Swift to ask for her permission to use Shake It Off in her new movie Little Monsters.

In the independent Australian comedy, the Oscar-winning actress plays Miss Caroline, a kindergarten teacher who must keep her class alive when zombies break out of a military testing facility and wander to the nearby petting zoo, where they are on a school trip.

Miss Caroline can usually be found playing the ukulele to entertain her youngsters and their particular favourite is Swift’s 2014 hit single. However, director Abe Forsythe struggled to get the rights to the song at a price the production could afford, so Nyong’o stepped in and made it happen.

“We tried for months and months and months to get the rights to it with no luck,” Forsythe explained to Vulture. “We tried reaching out to Taylor herself; didn’t get through. We tried her management. We tried her record company. Management I think came back at one point and said, ‘It will cost this,’ and it was like completely unaffordable for the type of movie we were.

“Anyway, when Lupita came onboard, Shake It Off was one of the things that appealed to her about Little Monsters, too. The song played a really particular role in one part of her life, so she really resonated with that being in the script. She was like, ‘We can’t not have this in the movie,’ so she told me she was going to write Taylor an email and not give Taylor the opportunity to turn her down... The only reason that song is in the movie is because Lupita is in the movie. I wouldn’t have been able to make the movie that we made with anyone else.”

Forsythe went on to explain that he wasn’t aware of the song but wrote it straight into the script after he heard children from his son’s school perform it on a ukulele at a recital.

Little Monsters in U.K. cinemas now.