The filler neck of a fuel tank with an arrangement for preventing incorrect fueling has a rotatable ring and closing elements which are actuated by said ring, with a transmission device having the following features being arranged between the movable part and the rotatable ring: there are two slides which are situated opposite one another and which have run-on faces which face toward one another in the support body, the two slides are connected to one another by means of a rigid bar, which rigid bar is movably articulatedly connected with its first end to the first slide and with its second end to the second slide, the second end of the bar is a bolt which engages into a first slot of the second slide and into a second slot of the rotatable ring.