According to Us Weekly, Gellar mistook Michael for Boy George, writing, "Do you really want to hurt me? I guess you do 2016 #ripboygeorge."
Gellar has since deleted the tweet and corrected herself after other Twitter users pointed out the mistake, promising that her "intentions were good."
For all concerned, Boy George (known for leading the hit group Culture Club) is 55 and very much alive.
The singer even shared his own touching tribute to Michael, writing, "He was so loved and I hope he knew it because the sadness today is beyond words. Devastating. What a beautiful voice he had and his music will live on as a testament to his talent."