Method for producing a construction element, in particular a tunnel element, from a curing material, such as concrete, in a mold, said construction element being provided with a watertight seal on at least one side thereof, wherein a gasket is used comprising a deforming body which is produced from a yielding material, such as rubber. According to the invention a base is produced from a relatively strong material, which base may or may not be detachable from the deforming body. Said base with or without said deforming body is placed against an inner side of the mold, said curing material is cast in the mold, and said curing material is cured to form said construction element with said watertight seal.