Demi Lovato has had to cancel her appearance at VH1's Philly 4th of July Jam due to tonsillitis. Hunter Hayes will step in for the "X Factor" judge during the Independence Day concert.

The "Made In The USA" singer had been slated to perform at the Kevin Hart-hosted show, which now includes "Wanted" singer Hayes, as well as performances from John Mayer, J.Cole, Ne-Yo, Jill Scott, Grace Potter and The Roots, who will serve as the event's house band.

Prior to the announcement that Hayes would be filling in for Lovato, she tweeted that she wasn't feeling well. "Sucks being so sick when you're alone and away from home," she wrote late Tuesday night. "Someone... come hold meeeeee... And bring me soup!!!"

Fans can tune into the event on Thursday, July 4 at 8 p.m. ET. You can also stream the show online at VH1.com and check Twitter for all the latest updates via the hashtag #PhillyJam.

Hunter Hayes Is Telling 'The Rest Of The Story' On Encore

Hayes recently played New York City's Webster Hall as a part of MTV's Artist To Watch LIVE series. He also just dropped his latest album, Encore, which features his single, "I Want Crazy." "This is an update. It's not brand-new, but it's just the rest of the story," Hayes told MTV News about the re-release of his self-titled debut album. "[It's] the summary of everything and the closing of the chapter."

Demi Lovato Previews 'Mortal Instruments' Track 'Heart By Heart': Listen Now!

Later this year, Hayes will headline the 12th annual CMT on Tour, billed as the Let's Be Crazy Tour. It all kicks off October 10 in Knoxville, Tennessee, with dates slated through December.