Olivia Rodrigo’s debut album Sour is finally here, released on Thursday, May 20, and a surprising name pops up in the album’s credits.

That name: none other than Taylor Swift, with the “Cardigan” singer receiving a writing credit on the Sour track “1 Step Forward, 3 Steps Back”. Also listed is Swift’s longtime producer, Jack Antonoff.

That, reports Rolling Stone, is because the song “is a nod to Swift’s lucky number, 13 and was inspired by ‘New Year’s Day’ from Swift’s 2017 album, Reputation.”

RELATED: Olivia Rodrigo Details Handwritten Letter From Taylor Swift: ‘You Make Your Own Luck’

As the magazine points out, neither Swift nor Antonoff actually contributed to the song, despite being listed on the credits.

Rodrigo has made no secret of being a hardcore Swiftie.

Ealier this year, Swift took to Instagram Stories to praise Rodrigo’s hit single “Drivers License”, writing, “I say that’s my baby and I’m really proud.”