A system malfunction led to the wrong anthem being played before Aston Villa's Champions League quarter-final second leg against Paris St-Germain.
The Europa League anthem was played over the PA system as the players lined up at Villa Park on Tuesday, before it was switched for the Champions League anthem.
Club and Uefa sources say the automated system responsible for playing the anthem crashed and was overriden by another system.
Several players looked quizzically at each other as the anthem was played.
Villa defender Ezri Konsa did a facepalm gesture as he and midfielder Youri Tielemans tried to contain their laughter, while PSG's Fabian Ruiz and Ousmane Dembele exchanged puzzled glances.