A method and a casting mold for producing an optical semiconductor module is provided, wherein a semiconductor body having at least one optically active element on its top is introduced into a leadframe. Then conductive connections are established between the semiconductor body and the leadframe, and then the leadframe and semiconductor body are encapsulated in a casting mold. Wherein provided in the part of the casting mold that faces the top of the semiconductor body are masking bodies, which extend from the top inner wall of the casting mold towards the optically active elements and cover the elements with their respective end face in a way that seals out casting material.