Swifties in attendance at Taylor Swift‘s second Chicago stop of the Eras Tour got a special surprise courtesy of country star Maren Morris.

Towards the end of Swift’s show on Saturday (June 3), the singer stopped to address her audience and offer them a never-before-seen treat. “Tonight, I’m gonna play a song I’ve never played live before,” she said according to a fan-captured video. “When I was re-recording Fearless, I thought it would be really cool to have one of my favorite artists sing on one of the songs ‘From the Vault.’ We are so lucky Chicago … because not only did that artist say ‘yes,’ but Maren Morris is actually here tonight.”

The “My Church” singer appeared on stage soon after, to uproarious applause from the audience. Both wielding their acoustic guitars, the duo launched into “You All Over Me,” a fan-beloved “From the Vault” track off of Fearless (Taylor’s Version). Bringing the plaintive country ballad to life for the first time in front of a live audience, Swift and Morris stood center stage and let their delicious harmonies wash over the eager crowd.

Fans in the audience weren’t the only ones delighted at Morris’ surprise appearance on stage — the singer took to her Instagram shortly after the show to express her gratitude to both Swift and the audience for having her. “We finally got to play ‘You All Over Me’ and I won’t ever be shutting up about it,” Morris wrote under a black-and-white photo of her and Swift performing together. “Love you @taylorswift and love you always, Chicago.”

Morris is far from the only surprise guest Swift has brought out during her Eras Tour stops around the country — in New Jersey, Ice Spice appeared to perform her remix of “Karma” for all three nights of Swift’s MetLife Stadium mini-residency, while past shows have featured guests like Marcus Mumford, Aaron Dessner and Jack Antonoff.

Check out Morris’ Instagram post, and some fan-captured videos of the performance below: