(WJHL) — Singer-songwriter Jason Isbell, the headliner of next month’s Bristol Rhythm & Roots Reunion, says concertgoers will need to show proof of COVID-19 vaccination or a negative test result in order to attend any of his future shows.

In a tweet Monday, Isbell said the requirement will apply to indoor and outdoor shows and that he will not play at any venues that will not allow that.

In a later tweet, the country artist said the requirement will be “for all our scheduled performances…”

Bristol Rhythm & Roots Reunion is set for Sept. 10–12 with Isbell and his band, The 400 Unit, scheduled to take the stage on Sunday, the festival’s final day. He is also scheduled to play at Bonnaroo early next month.

News Channel 11 has reached out to Bristol Rhythm & Roots for comment.