A stair system for a working machine having an upper carriage and a lower carriage pivotable against each other includes a foldable ladder movable between an upper end position and a lower end position, wherein in the upper end position the ladder is arrangeable at the working machine in a way that moving and pivoting of the working machine is not disturbed and wherein in the lower end position the ladder is able to provide access to the upper carriage, such as to a cabin, of the working machine; a control system comprising at least one alignment sensor indicating alignment of the upper and lower carriage and a controller which is able to block or enable a movement of the foldable ladder based on an output of the alignment sensor.