Popular a cappella group Pentatonix is set for its first network holiday special, which will air December 14 on NBC. A Pentatonix Christmas Special marks the quintet’s return to NBC, where they first rose to fame as Season 3 winners of the network’s a cappella singing competition The Sing-Off.

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In their hourlong NBC special, the Grammy-winning, multiplatinum Pentatonix will be joined by Reba McEntire and Kelly Clarkson, with other special guests to be added at a later date. That might include Dolly Parton, whose recent cover of her 1974 song “Jolene” with Pentatonix has gone viral, giving the country star a Top 20 hit for a sixth consecutive decade. Parton has a strong relationship with NBC where she has a deal for TV movies based on her songs.

A Pentatonix Christmas Special is executive produced by Brad Lachman Productions, Inc. in collaboration with RCA Records and Pentatonix.

Pentatonix recently released their third holiday album, A Pentatonix Christmas, which debuted at No. 3 on the Billboard 200. The album features the group’s arrangement of the Leonard Cohen classic, “Hallelujah,” which debuted at No. 6 on Billboard’s Digital Songs chart. The music video received more than 20 million views in its first week (watch the video below). The group is on the final leg of its 2016 world tour.