A valve housing for a check valve comprises a housing body for mounting a pair of flapper elements and a pair of valve openings extending through said valve body. The valve openings are separated by a web which extends from one side of the valve body to an opposed side of the valve body. The valve body and web define sealing surfaces around the valve openings on one face of the valve housing. The web comprises a slot extending into the web from a face thereof on said one face of said valve housing and extending along a length of the web.