A first connecting part for a plug-in connector, the first connecting part being configured for being mated with a second connecting part of the plug-in connector in a mating direction, the first connecting part comprising - at least one latching element configured for engaging with at least one counterlatching element of the second connecting part when the first connecting part is mated with the second connecting part, - a locking member movably arranged in the first connecting part, wherein the locking member is configured for locking an engagement between the at least one latching element and the at least one counterlatching element in a locking position of the locking member, - with the at least one latching element being configured for engaging with the at least one counterlatching element when the locking member is in a non-locking position, characterised in that - the first connecting part comprises a forced guidance configured for enforcing a rotational motion of the locking member when the locking member is moved relative to the at least one latching element, - wherein at least one surface of the locking member is shaped and configured for interacting with at least one surface of the second connecting part such that a rotational motion of the locking member relative to the first connecting part is enforced by the interaction between the at least one surface of the locking member and the at least one surface of the second connecting part 2 and by the forced guidance, when the first connecting part is mated with the second connecting part, wherein the rotational motion comprises moving the locking member from the locking position to the non-locking position and back to the locking position. - at least one latching element configured for engaging with at least one counterlatching element of the second connecting part when the first connecting part is mated with the second connecting part, - a locking member movably arranged in the first connecting part, wherein the locking member is configured for locking an engagement between the at least one latching element and the at least one counterlatching element in a locking position of the locking member, - with the at least one latching element being configured for engaging with the at least one counterlatching element when the locking member is in a non-locking position, characterised in that - the first connecting part comprises a forced guidance configured for enforcing a rotational motion of the locking member when the locking member is moved relative to the at least one latching element, - wherein at least one surface of the locking member is shaped and configured for interacting with at least one surface of the second connecting part such that a rotational motion of the locking member relative to the first connecting part is enforced by the interaction between the at least one surface of the locking member and the at least one surface of the second connecting part 2 and by the forced guidance, when the first connecting part is mated with the second connecting part, wherein the rotational motion comprises moving the locking member from the locking position to the non-locking position and back to the locking position.