jumpspell difficulties

Hey! About the jump spell. Its kind of annoying when giants/barbs/other land-units still target the targets they would target before the jump spell was dropped.
For example: A defensive building is behind a wall, and you drop a jump spell, and some giants there. And the giants still target the closest target OUTSIDE the walls, eventhough this defense behind the wall is alot closer. ( no walls between the giants and this target )
What i mean is that, the units should act like there are no walls in the jump spell circle at all.