An 
elevator includes a first 
elevator unit vertically movable in a hoistway, and a second 
elevator unit vertically movable in a hoistway. At least one of said elevator units is an elevator car. One or more belt-shaped hoisting ropes interconnects the first elevator unit and the second elevator unit. A 
drive wheel is provided for moving said one or more belt-shaped hoisting ropes. Each of the belt-shaped hoisting ropes passes around the 
drive wheel and includes consecutively a first 
rope section extending between the 
drive wheel and the first elevator unit, and a second 
rope section extending between the drive wheel and the second elevator unit. The elevator further includes non-driven cambered diverting wheels, each said first 
rope section being arranged to pass around a first cambered diverting wheel, in particular resting against a cambered circumferential surface area thereof, and each the second rope section being arranged to pass around a second cambered diverting wheel, in particular resting against a cambered circumferential surface area thereof. A rope monitoring arrangement is configured to monitor displacement of each of the first rope sections in the axial direction of the wheels away from a predefined zone, and displacement of each of the second rope sections in the axial direction of the wheels away from a predefined zone. The elevator is configured to stop the rotation of the drive wheel when one or more of the first and second rope sections is displaced in the axial direction of the wheels away from a predefined zone.