The plug connector part 2 furthermore comprises a locking element 24. The locking element 24 is formed integrally with the contact carrier 21, alternatively firmly mounted thereon. The locking element 24 projects in parallel to the plug-in axis S from the contact carrier 21, specifically from its base. A part of the locking element 24 is accommodated in a guide 220 of the sliding sleeve 22. The guide is formed as a slot aligned in parallel to the plug-in axis S. The locking element 24 has actuating surfaces, here in the form of bevels 240. For this purpose, the sliding sleeve 22 has suitably arranged actuating surfaces, here likewise in the form of bevels 222. The bevels 222 of the sliding sleeve 22 are arranged at an end of the sliding sleeve 22 (facing the mating plug connector part 3 in the plugged state). If the sliding sleeve 22 is moved in relation to the contact carrier 21 such that the bevels 240, 222 come into contact with one another and slide along one another, an end section of the locking element 24 (substantially perpendicular to the plug-in axis S) is lifted.