Valencia will protest to Uefa after a referee did not award a goal in their Champions League Under-19 penalty shoot-out against Chelsea.
Adrien Jaccottet thought Alberto Gil's penalty hit the post, but replays show it rebounded from inside the goal.
Chelsea scored with all their five penalties to go through after the game finished 1-1 in normal time.
The Valencia players and staff urged the Swiss referee to consult with the television replay at Chelsea's Cobham training ground, but it is believed he refused.
In a statement, the La Liga side, who scored with their three other penalties in the shoot-out, urged their young players: "Do not lose your confidence and your faith in football because of this incident.
"We are confident that Uefa will give an appropriate response to that required by the situation."
Reigning champions Chelsea will host Lyon or Ajax in the next round, which is due to be played on 8-9 March.