UEFA's head of referees says goalkeepers who leave their line and save a penalty should get a yellow card and the kick ordered to be retaken.
Pierluigi Collina says a strict interpretation of the rules was stressed to European Championship referees at Friday's debriefing before the knockout rounds where penalty shootouts are a factor.
Collina says "it was a mistake, unfortunately it happens" that Croatia goalkeeper Danijel Subasic was allowed to advance far from his line to save a penalty kick by Sergio Ramos of Spain.
Subasic's save kept the score 1-1 and Croatia went on to win 2-1 and top their group.
Collina says, if the situation is repeated, the penalty "will be retaken and the laws of the game say the goalkeeper will be cautioned."