Amazingly, ABBA may have just performed together for the first time in three decades.

The four members of the mega-selling Swedish pop group came together on Sunday at a private party at the Berns Salonger hotel in downtown Stockholm, according to Billboard. Agnetha Fältskog, Björn Ulvaeus, Benny Andersson and Anni-Frid Lyngstad reportedly embraced onstage and even performed together, although no footage of the performance has surfaced thus far.

The star-studded event was a celebration of the 50th anniversary of the pop quartet, as Ulvaeus and Andersson began writing together in 1966. ABBA hasn’t performed together since 1986, although hits like “Mamma Mia” and “Dancing Queen” live on, and the quartet was inducted into the Rock and Roll Hall of Fame in 2010.

ABBA also briefly reunited earlier this year at the Mamma Mia! The Party launch in Stockholm in January. There’s no word on any further reunion following Sunday night.