An electrical connector includes a housing extending from a mating face to an opposite face, and first and second side walls that extend between the mating face and the opposite face. The housing has a contact cavity that includes opposing sides. The first side wall includes a side opening that extends through the first side wall into communication with the contact cavity. The contact cavity is accessible through the mating face for receiving a mating connector therein. Electrical contacts are held by the housing and arranged in opposing rows that extend along the opposing sides of the contact cavity. A retention insert is received within the side opening. The retention insert includes fingers that extend into the contact cavity and engage in physical contact with corresponding electrical contacts of one of the rows of the electrical contacts to hold the corresponding electrical contacts within the contact cavity.