The invention relates to an assembly for a turbojet engine which includes a pylon (1) and a nacelle supported by said pylon (1). Said nacelle (3) includes a grid thrust reverser (21) including an integral cowl mounted so as to slide on rails (15), which are arranged on both sides of said pylon (1), between a direct jet position and a thrust reversal position. Said assembly is characterized in that it includes means (23, 31) for blocking the sliding movement of the cowl on the rails (15), said means being inserted between the pylon (1) and the cowl.