A filler neck for a fuel tank of a motor vehicle is provided. The filler neck comprises a filler pipe with a longitudinal axis and a circular cross section with an inner diameter. The filler neck further comprises a blocking element that is arranged inside the filler pipe and extends only inside a circle sector of a circle concentric to the circular cross section. The circle has a circle diameter that is smaller than the inner diameter. The circle sector has an angle at the center of less than 180°.