Gwen Stefani won't be able to perform in Las Vegas on Wednesday night (July 24) due to an unspecified illness. The pop singer and girlfriend to Blake Shelton shared the disappointing news on Instagram.

"I am so upset to share that I am unwell & will not be able to perform my Vegas residency show tomorrow night," Stefani writes. "I was so looking forward to seeing everyone & performing & I wish I wasn't feeling the way I do. To everyone who was coming to Wednesday's show, I am so sorry. I am doing everything I can to be back on stage Friday."

Watch: Jimmie Allen Is Feeling "Unwell" Too!

Stefani announced the Just a Girl Las Vegas residency at the Zappos Theater would begin in June 2018 and run through mid-March of 2019 but she's since extended the show into November. She's been busy in the recording studio in recent years, having recorded her first new album of studio material in a decade in 2016 and following with a Christmas album that featured Shelton.

The pair will celebrate four years together in November and speculation of marriage has been with them since nearly the beginning — even Garth Brooks has gotten in on putting pressure on the "God's Country" singer! It's now a matter of "when" not "if" he admits.

"It’s kind of a blur," he told People earlier this month. "It still feels like it’s pretty new to me. I guess it is, relatively. Four years isn’t forever, but man, it seems like it just happened in no time."

Blake + Gwen Are Adorable In These Pictures!