An arrangement is provided for controlling a variable position of vanes at a turbine in a flow channel of a turbine. The arrangement includes a nozzle ring carrying a set of vanes, each of the vanes being connected to a vane pin housed in the nozzle ring. A rotational position of the vanes is accomplished via a vane displacement drive train including a pivotally supported pivot axle, a first actuator arm arranged on the pivot axle, which first arm is connectable to a drive actuator, a second actuator arm arranged on the pivot axle, which second arm is connected to a pin engaged with an unison ring for pivoting the unison ring, and a vane arm being connected to each vane pin and the unison ring for displacement of the vanes via pivotal displacement of the unison ring, and wherein a stop screw is arranged for limiting the pivotal displacement of the vanes.