A skylight assembly for installation in a vehicle wall includes a lens body having an exterior surface and a cap connected to an end of the lens body and a lens flange. There is a nut member to secure the lens body. A gasket is disposed between the lens member and the vehicle wall and includes a first leg portion and a second leg portion. The first leg portion extends into a recess between a surface of an aperture in the wall and the exterior surface of the lens body and the first leg portion has a uniform thickness which is less than a width of the recess thereby forming a gap. The second leg portion extends from the first leg portion substantially at a right angle and is disposed between and in contact along its length with the lens flange and the exterior of the wall about the aperture.