Rod Stewart is to perform with the X Factor semi-finalists on Sunday's (02.12.12) show.
The former Faces lead singer will sing with the four remaining acts - James Arthur, Jahmene Douglas, Christopher Maloney and boy band Union J - on this weekend's group song, the first time a star has sung with the contestants on this year's series.
Rod and the wannabes will sing a festive tune taken from his new album, Merry Christmas, Baby.
An insider told The Sun: "It is a big coup to get Rod - and to get him to perform with the contestants.
"He is an absolute legend and is a big fan of the show. He jumped at the chance of being able to perform."
Show chiefs had been hoping to keep the singing a surprise as the contestants have not yet been told.
Before hearing the news, Union J tweeted: "Group ensemble this week is gonna be amazing and great fun :) so excited to perform it. (sic)"
Meanwhile, all the semi-finalists have recorded the song they'll release if they win the show, but only the top two will get the chance to perform it in the Manchester final on 9 December.
Arthur, Union J, Douglas and Maloney recorded different tracks several weeks ago, and while the songs are a closely-guarded secret, show chief Simon Cowell has given Union J Demi Lovato's Skyscraper.
This year the proceeds from the winner's song will go to children's charity Together for Short Lives.