An electrical connector includes: an insulative housing having a front tongue with two opposite surfaces; an upper and lower rows of contacts with contacting portions exposed to the two opposite surfaces of the tongue; and a primary shell enclosing the insulative housing to together with the tongue define a mating chamber, wherein the insulative housing includes a pair of side steps and a pair of side protrusions; and the primary shell includes a pair of side wings sitting on the pair of side steps, each side wing having a notch engaging a corresponding side protrusion.