A locking-aid device is disclosed for a lock, especially for a vehicle door lock or flap lock, in which a pneumatic single-acting locking-aid drive is provided for displacing an abutment for a rotary latch out of a catch position into a locking position, in which the abutment is secured positively by means of a detent pawl. According to the invention the detent pawl can be lifted out, during the opening of the lock, independently of a movement of the locking-aid drive by means of an operative connection. This can be brought about purely mechanically or by means of a separate drive for lifting out the detent pawl during the opening of the lock, so that the abutment can always jump into its catch position immediately during or after the opening of the lock and thus also allows a successive multiple activation of the locking-aid assistance.