A milking robot system for milking of a dairy animal with teats includes milking cups, a robot arm for attaching the milking cups to the teats, a teat detector configured to detect the position of the teats, and a compressed air system for providing dry compressed air to at least part of the milking robot system. The teat detector comprises a housing containing an optical sensor. The compressed air system is operatively connectable with the inside of the housing via an air line in order to at least partly replace air which is present in the housing by an amount of dry air from the compressed air system. This replacement operation may be performed directly, under pressure, or by first extracting air by means of an additional system and then replenishing it with dry air from the compressed air system.
