An arrangement in a rotary milking system includes a rotating platform, an entry thereto and an exit therefrom. A selection gate arrangement at the exit of the rotating platform selectively guides animals, which have been milked in the rotary milking system and leave the rotating platform through the exit, back to the entry of the rotating platform or to a waiting area. A control device is provided for (i) determining whether an animal, which has been milked and leaves the rotating platform through the exit, has at least one udder compartment that was incompletely milked the last time the animal was milked, and (ii) controlling the selection gate arrangement to guide the animal back to the entry of the rotating platform or to the waiting area provided that the animal has at least one udder compartment that was incompletely milked the last time the animal was milked.
