A lifting unit (1) to lift the rear part of a hood or bonnet in the event that an accident should arise comprises an inner cylindrical guide (2) to receive gas from a gas generator and telescopically mounted on the guide, to telescopically interconnected cylindrical piston elements (12, 17). There is a certain degree of play between the telescopically interconnected units to facilitate a virtual pivoting movement of the hood or bonnet to be lifted by the lifting unit.