Abstract: A device to stop a knitting machine when a needle hook has broken. The device consists of a directed blast of air at the needles of a knitting machine as the needles pass the point on the machine where an existing electronic detector device stops the machine upon indication that the needle latch is in the closed position. The blast of air raises the latch of a broken needle to the closed position to activate the detector. The latch of a needle in normal working order is restrained in the open position at the detector location by the action of a loop of yarn about the latch and is not affected by the blast of air. With a needle controlled to form a tuck stitch a broken needle hook which fails to catch a loop of yarn will result in an open latch condition which does not activate any detector in a conventional machine equipped only with a closed latch detector.