Veteran country singer John Anderson has canceled his headlining appearance at an upcoming festival in Alabama, citing "serious medical issues."

Anderson was scheduled to top the bill at the Main Street Music Festival on Saturday (Aug. 5) in Albertville, Ala. On Tuesday (Aug. 1) festival organizers broke the news via Facebook, sharing a statement from Anderson's reps that reads:

Due to unforeseen and serious medical issues, John Anderson will not be appearing August 5th in Albertville, AL.
He will remain, for the time being, under the direct care and supervision of a Nashville area doctor.
John is deeply saddened to not be able to perform for his friends in Alabama, and hopeful he will begin healing soon.

"The Main Street Music Festival Committee extends our warmest wishes, thoughts, and prayers to John at this time and is hoping he makes a full and quick recovery," the festival adds.

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Anderson has placed more than 40 singles on the country charts since he debuted in 1977, including five No.1 hits with "Wild and Blue," "Swingin'," "Black Sheep," "Straight Tequila Night" and "Money in the Bank." He released his latest album, Goldmine, in 2015 on the Bayou Boys Music label. Anderson was inducted into the Nashville Songwriters Hall of Fame on October of 2014. No further information is available about his illness. The singer has not addressed the cancellation via social media.

Though Anderson won't be able to perform, the show will still go on. Craig Morgan is set to take Anderson's place as the headliner for the Main Street Music Festival on Saturday night, bringing a long string of hits to the stage including "Bonfire," "Almost Home," "Redneck Yacht Club," "International Harvester" and "That’s What I Love About Sunday."

The Main Street Music Festival kicks off Friday night (Aug. 4) with headliner Bret Michaels. For more information, visit the festival's website.

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