A connecting plug includes a locking pin arranged at a connector face. The locking pin has at least one latching element and a counter-piece. The latching element is configured for engaging with at least one counter-latching element of a second connector part. The locking pin includes a spring element configured for resiliently pressing the at least one latching element and the counter-piece against each other. The counter-piece is shaped and configured for pressing the at least one latching element in a radially outward direction and for positively locking the at least one latching element in an engaged position as soon as the at least one latching element is engaged with the at least one counter-latching element.