A synchronous machine, in particular a generator for a vehicle, has an excitation system with a plurality of electrically excited individual poles in a rotor, preferably in form of claw poles excited by at least one common excitation coil, in which for compensation of a magnetic stray flux, in the free spaces between the axially oriented claw poles permanent magnets are inserted at the axial ends of the pole plates of the rotor, so that the permanent magnets are supported by a holder against centrifugal forces and held by it, and therefore an especially simple and inexpensive holder is formed which considerably simplifies and facilitates the insertion of the permanent magnets.