An attachment for a light string having sockets for respectively receiving therein bulb assemblies and wires extending out of the sockets includes a body. The body of the attachment has a through hole defined through the body and a fastener slot defined in the body. A cord is able to extend into the through hole and is fastened in the fastener slot. The cord is held securely in the body of the attachment of each socket so when a force acts on the Christmas light string, the Christmas light string has enough strength not to break.