A planetary gear of a differential gear, with a planetary carrier to which planetary wheels are rotatably connected and which are in meshing operative contact with at least one sun wheel, whereby the planetary carrier is connected to a driving wheel, further comprising a roller bearing that is provided with two bearing rings, a bearing inner ring and a bearing outer ring for axial and/or radial position determination of the planetary carrier relative to a fixed housing, wherein a cover is positioned radially between the planetary carrier and the sun wheel.