surprised ' Bonnaroo audience on Thursday, June 12, for an "absolutely fire" duet between country "icons."

In a new video uploaded to the "Mama's Broken Heart" singer's Instagram account on Friday, the two duetted on Combs' "Outrunnin’ Your Memory" during the latter's headlining timeslot at the southern music festival—the first country artist to ever headline the festival, according to Lambert.

"Last night at @bonnaroo with @lukecombs. Thanks for sharing your stage Luke and congrats on being the first country artist to headline the festival 🤠🩵," she captioned the clip.

Fans were unanimously "obsessed" with the unexpected duo, with one fan gushing, "Oh man so good 👏 top notch vocals right there."

"You sound terrific together - such a fan of you both!👏🔥👏🔥🙌," one commenter praised.

"the voices of these two individually are incredible but TOGETHER 🔥 one of my fave collabs!" another declared.

"Obsessed with this duo, this song, & that outfit 🙌 t-shirt with a splash of fringe? Yes please 🫡💖," someone else wrote.

Lambert's followers continued to gush over the "ICONIC" duo's performance, with one calling it "Absolute 🔥."

"One of my absolute favorite songs that should have been a number one hit!! It's beautiful 🔥🙌❤️😍," someone else fawned.

"Luke combs just made this song 20x more electric," another said, as someone else commented, "Never outrunnin’ this one! Obsessed 🤩."

"Loved watching this on live last night I wish I was actually there lol😭🫠❤️❤️," a remote viewer admitted.

Related: Miranda Lambert Sneakily Blends In on the Dance Floor While Surprising Fans at Local Bar