Electric plug connector having (a) a plug connector housing with a front opening provided for plugging in a mating plug connector, a rear end facing away from the front opening, at least one receptacle for an electrical contact element, and with a primary securing device which is designed and arranged in order to latch on to the contact element when the contact element is situated in an axial end position in the receptacle; (b) a secondary securing device which, in a securing position (Ps), positively blocks the latching between the primary securing device and the electrical contact element, wherein the plug connector housing has a guide for the secondary securing device which is provided in such a way that the secondary securing device can be introduced into the plug connector housing through the front opening, wherein the secondary securing device is situated in a starting position (P A) in the plug-in path of the mating plug connector, and wherein the secondary securing device can be displaced into the securing position (Ps) in the direction of the rear end of the plug connector housing in such a way that, in the securing position (Ps), the secondary securing device frees the plug-in path for the mating plug connector, and wherein the plug connector housing has a multi-part design and has at least one outer housing shell and one inner housing shell arranged inside the outer housing shell, wherein the inner housing shell has the at least one receptacle, and wherein the guide for the secondary securing device is formed on the inner housing shell, characterized in that the secondary securing device latches in place in the starting position (P A) inside the plug connector housing such that the secondary securing device can be made available securely in the plug connector housing until the secondary securing device is finally used for positively blocking the primary securing device. (a) a plug connector housing with a front opening provided for plugging in a mating plug connector, a rear end facing away from the front opening, at least one receptacle for an electrical contact element, and with a primary securing device which is designed and arranged in order to latch on to the contact element when the contact element is situated in an axial end position in the receptacle; (b) a secondary securing device which, in a securing position (Ps), positively blocks the latching between the primary securing device and the electrical contact element, wherein the plug connector housing has a guide for the secondary securing device which is provided in such a way that the secondary securing device can be introduced into the plug connector housing through the front opening, wherein the secondary securing device is situated in a starting position (P A) in the plug-in path of the mating plug connector, and wherein the secondary securing device can be displaced into the securing position (Ps) in the direction of the rear end of the plug connector housing in such a way that, in the securing position (Ps), the secondary securing device frees the plug-in path for the mating plug connector, and wherein the plug connector housing has a multi-part design and has at least one outer housing shell and one inner housing shell arranged inside the outer housing shell, wherein the inner housing shell has the at least one receptacle, and wherein the guide for the secondary securing device is formed on the inner housing shell, characterized in that the secondary securing device latches in place in the starting position (P A) inside the plug connector housing such that the secondary securing device can be made available securely in the plug connector housing until the secondary securing device is finally used for positively blocking the primary securing device.