If Julian Alvarez slips while taking a spot kick for Atletico Madrid at the Club World Cup this month, he will get the second chance he was denied in the Champions League in March, after international football's rule-making body on Tuesday clarified the double-touch rule.
Football's rule-making International Football Association Board (IFAB) announced that if players unintentionally touch the ball twice while taking a spot kick and still find the net, they should be allowed a retake.
Alvarez slipped as he netted his penalty kick in a shooutout to decide a Champions League Madrid derby.
Video review (VAR) detected that he touched the ball twice and the referee ruled the shot a miss under Law 14, which deals with the penalty kick. Real went on to win 4-2.
After the match, European governing body Uefa said that "under the current rule, the VAR had to call the referee signalling that the goal should be disallowed".
Uefa said it would hold talks with world football's governing body Fifa and and the rule-making International Football Association Board (IFAB).
On Tuesday, IFAB issued its ruling. It was to come into force on July 1, but Fifa at once announced the change would apply to the Club World Cup, which kicks off in the United States on June 15 with both Madrid clubs among the 32 teams.
"The situation where the penalty taker accidentally kicks the ball with both feet simultaneously or when the ball touches the penalty taker's non-kicking foot or leg immediately after they have taken the kick... is rare," wrote Lukas Brud, IFAB's secretary in a circular.
"As it is not directly covered in Law 14, referees have understandably tended to penalise the kicker for having touched the ball again," he wrote.
However, he added, the law "is primarily intended for situations where the penalty taker deliberately touches the ball a second time before it has touched another player".
"This is very different from the penalty taker accidentally kicking the ball with both feet simultaneously or touching the ball with their non-kicking foot or leg immediately after they have taken the kick, which usually occurs because they have slipped."
Brud pointed out that even an accidental second touch could be unfair to a goalkeeper because it changes the ball's trajectory.
Therefore, he wrote, IFAB had decided that "if the kick is successful, it is retaken".
If a kick during the game is unsuccessful, the result is an indirect free kick, as it would be for a deliberate second touch, unless the referee decides to play an advantage for the defending team. In a shootout it remains a miss.