Abstract: A mortise lock for a door is provided, including an automatic deadbolt mechanism for automatic projection of a deadbolt mounted in the lock housing form a retracted to an extended position upon closing of the door. The automatic deadbolt projecting mechanism for use in the mortise lock comprises a blocking element adapted to be pivotally mounted in the housing for movement relative to the housing between a first position where a blocking surface is adapted to engage the deadbolt for holding the deadbolt in the retracted position against the force of a deadbolt biasing means and a second position where the blocking surface does not engage the deadbolt. The blocking element is pivoted to the second position upon door closing by operation of internal, pivoting lock components, including a sensor adapted to be mounted in the housing for movement relative to the housing between an extended position and a retracted position.