A seat back hinge mounting for a forwardly foldable motor vehicle seat having a first hinge arm and a second hinge arm adapted for relative rotation about a hinge pin. A locking cam is disposed on said second hinge arm and is movable between a locking position and a release position. A first stop flange and a second stop flange are provided on the first hinge arm. The locking cam cooperates with the second stop flange in the locking position and has come free from said second stop flange in the release position. A retainer lug, which is bound by said first stop flange and by said second stop flange in the circumferential direction, is provided on the first hinge arm. A limit stop cooperating with the first stop flange and being spaced the same radial distance apart from the hinge pin as the first stop flange is disposed on the second hinge arm. A retainer device prevents the locking cam from moving from the release position into a region which on the one side is located between the first stop flange and the retainer lug and which on the other side is defined by an arc of a circle about the hinge pin and by the radius of the free end of the retainer lug.