Solange Knowles revealed Wednesday that she’s been struggling with an autonomic disorder that prompted her to pull out of an upcoming New Year’s Eve performance.

“The past five months I have been quietly treating, and working through an Autonomic Disorder. It been a journey that hasn’t been easy on me…” she wrote on Instagram.

The artist did not share what type of autonomic disorder she was diagnosed with, but the term refers to a breakdown of the autonomic nervous system, which controls involuntary bodily functions.

“Sometimes I feel cool, and other times not so cool at all. It’s a complicated diagnoses, and I’m still learning so much myself, but right now, my doctors are not clearing me for such an extended lengthy flight, and doing a rigorous show right after.”

Because her doctor’s concerns, she said, she had to cancel her performance at the Afropunk Festival on New Year’s Eve in Johannesburg, South Africa.

“I give you my ABSOLUTE WORD I will come back with AfroPunk and deliver this performance … ..as it is so extremely important to me to connect with the people who have so closely inspired me in so many ways,” Solange said.

The festival, which celebrates the influence of African American culture through music, film, skate and art, this year added Johannesburg to its multiple-city, multiple-country roster.

In a message shared on its official Facebook page, the festival’s organizers that they were saddened that Solange would be unable to perform this weekend, but underlined that her health was of the utmost importance.

“Her music and spirit has been a place of great comfort and inspiration to us as a community,” the statement read.