Abstract: A camshaft includes a device for hydraulic adjustment of a relative rotating position of the camshaft for the purpose of influencing valve timing. The device has a drive wheel, a cell wheel, and an impeller. The impeller is disposed by way of vanes within cells of the cell wheel and can carry out relative motion. A locking arrangement, which operates in the starting phase of the internal-combustion engine, is provided between the cell wheel and the impeller. The locking arrangement is formed by an axially spring-loaded, hydraulically operated piston housed in one of the vanes of the impeller and by a corresponding receiving device for the piston provided in a constructional unit consisting of the drive wheel and the cell wheel. The piston, which projects by way of a locking section into the receiving device and is guided in the vane, cooperates with an operating element for optimizing the locking arrangement.