There are two 'DRS' overtaking zones on Montreal's Circuit Gilles Villeneuve for the Canadian Grand Prix, but only one 'detection' point.
It will be the first time in 2011 that the adjustable rear wing system will be available to chasing drivers twice per lap in the race.
But the only 'detection' point will be at the exit of the tight hairpin, just before the first DRS zone begins on the long run down to the Wall of Champions chicane.
It means that if a driver was within 1 second of his prey at the hairpin, he will get another chance to pass him in the second DRS zone after the Wall of Champions.
Also, if he has already made the pass before the Wall, he will be able to trigger his wing in the second zone to pull away.
"You could actually lose two places," said McLaren driver Jenson Button. "If you're the lead car and there are two cars behind you, one of them can overtake on the first straight and the next can overtake you down the pit straight.
You could actually lose two places
"But maybe that will help us in the race. It could be fun," said the Briton.
Lewis Hamilton speculated about the reason for the FIA's decision to have just one detection point.
"I would assume (if there was two detection points) everyone would probably wait, just stay behind them and not even bother overtaking on the first DRS zone and wait for the last one," he said on Thursday.