The invention relates to an elevator comprising a hoistway; an elevator car vertically movable in the hoistway; a plurality of ropes connected to the car; a rotatable traction member comprising a circumferential traction surface area for each of the several ropes; each rope being arranged to pass around the rotatable traction member resting against a circumferential traction surface area of the traction member; drive machinery for controlling rotation of the rotatable traction member. The elevator comprises means for detecting displacement of each of the ropes over a first limit position of the rope in the first axial direction of the rotatable traction member, and over a second limit position of the rope in the second axial direction of the traction member; and in that displacement of one or more of said ropes in axial direction of the rotatable traction member over the first or second limit position is arranged to trigger the drive machinery to stop the rotation of the rotatable traction member.