The invention relates to a method of increasing the leak tightness of a mechanical connector of an extracorporeal blood treatment machine, wherein the mechanical connector has a pair of connection parts which have corresponding sealing surfaces, with at least one of the two sealing surfaces being wetted at least sectionally by a viscous fluid before the joining together of the connection parts and/or with the connection gap between the connection parts being covered by a sheath after their joining together. The invention further relates to an extracorporeal blood treatment machine comprising a mechanical connector which has a pair of connection parts which have corresponding sealing surfaces, with the sealing surfaces being at least sectionally wetted with a viscous liquid with a closed connector and/or with the connection gap between the connection parts of the closed connector being covered by a sheath.
