A fastener outlet assembly for a fastener driving tool includes: an outlet passage arranged to expel fasteners from the assembly to a workpiece during use, the outlet passage having one or more walls; and a detector arranged to detect whether a fastener is present in the outlet passage. The detector comprises at least part of a cover that provides at least part of a wall of the outlet passage, the cover being movable with respect to the remainder of the outlet passage to open the outlet passage and gain access thereto.