An electrical plug connector has a plug portion that extends to an integral medial annular flange that serves as a pilot and stop for a shroud of a mating electrical socket connector. The flange has a forward stop shoulder of reduced height that forms a ledge, and a pair of vertically spaced retainer lips that are integrally attached to the ledge and that extend forwardly of the ledge in an axial direction. The electrical plug connector includes an elastomeric interface seal for forming a seal between the plug portion and the shroud of the mating electrical socket connector that comprises an annular body and a plurality of flexible sealing lips that biasingly engage an inner surface of the shroud when the electrical plug connector is plugged in. The annular body of the elastomeric seal is mounted on the plug portion with its trailing axial end against the stop shoulder of the flange and beneath the retainer lips so that the elastomeric seal cannot ridge over the flange and bunch when the electrical plug connector is plugged into the mating electrical socket connector.