Andy Murray called it “irritating” and Nick Kyrgios said it was “stupid” as confused players at the Australian Open had to deal with spectators giving them Cristiano Ronaldo’s “siuu” celebration treatment. 

Football fans are used to seeing the Manchester United superstar launch into a mid-air pirouette before exclaiming “siuu” when he scores—which comes from Spanish and Portuguese words for yes. But for the uninitiated it sounds like “boo” and fans at the opening Grand Slam of the year were shouting it en masse during Murray’s and Kyrgios’s matches at John Cain Arena on Tuesday.