Rangers manager Gio van Bronckhorst was left baffled after Dejan Stankovic appeared to snub a post-match handshake.
The Premiership champions took a thumping 3-0 win in the first leg of their Europa League last 16 tie against Red Star, putting one foot in the quarter-finals.
Captain James Tavernier opened the scoring from the spot, before Alfredo Morelos smashed home on a set piece.
Veteran goalkeeper Allan McGregor came up big in Europe again as he saved Aleksandar Katai's penalty, diving low to his right for a stunning stop.
And centre-back Leon Balogun powered home a header on a second half corner to put his team firmly in the driving seat.
But it seems Red Star were in no mood to offer their congratulations as boss Stankovic appeared to snub the post-match handshake.
The former Inter and Lazio midfielder didn't hang around after the final whistle, with a bemused Van Bronckhorst left shrugging his shoulders as the Serb headed down the tunnel.
Red Star saw three goals correctly ruled out for offside but were fuming about the penalty awarded for a foul on Ryan Kent.
Referee Serdar Gozubuyuk initially waved away Rangers' appeals after a challenge from Slavoljub Srnic.
But the Dutch whistler was called to the VAR monitor and after watching the replay awarded the spot kick.
