The invention relates to an engine-control valve having a body defining an inner channel and including a flap (10) pivotably mounted by a pin (12), said flap (10) including a first portion (11) and being capable of pivoting between an open position enabling gas to flow into the channel, and a closed position preventing said flow, and in which the flap (10) engages with a planar seal (1) inserted between two elements of the valve body, said seal (1) having an outer contour surrounding the outer contour of the flap (10) on the outside and said seal including an opening (6) and a solid portion (3), said first portion (11) blocking the opening (6) of the seal (1) when the flap (10) is in a closed position, one of the two elements (20) of the body being provided with a supporting projection (21), positioned in the valve such as to be in contact with the solid portion (3) of the seal (1).
