A latch module for selectively engaging into a striking plate of a door jamb, comprising at least a housing, a latch bolt, a guard bolt, a blocking member and a stem, wherein - the latch module has a first end and a second end, wherein the first end is configured to face towards the door jamb and the second end is configured to extend into a mortise of a door, - the housing movably supports the latch bolt and the guard bolt, - the latch bolt and the guard bolt each have an extended and a retracted position and each are biased into their respective extended position, - the stem has a longitudinal axis and is movably supported relative to the housing and in that the stem has a closed position and an open position, - the stem is movably supported relative to the latch bolt, - the stem has a block configured to entrain an abutment of the latch bolt, if the stem reaches a first intermediate position while being moved from the stem's closed position towards the stem's open position, - the blocking member is movably supported between a blocking position ( α) and a released position ( α), and wherein the blocking member is configured • to block a retraction of the latch bolt, when in the blocking position and • to release blocking the retraction of the latch bolt, when the blocking member is in the released position ( α), - the guard bolt is configured to maintain the blocking member in the blocking member's released position, if the guard bolt is in the guard bolt's extended position, characterized in that (i) the blocking member comprises a first leg and a second leg, (ii) a front-end portion of the first leg is connected by a front hinge to the latch bolt, wherein the front hinge defines a front hinge axis, (iii) a rear end of the second leg is connected by a rear hinge to the housing, wherein the rear hinge defines a rear hinge axis, (iv) the front hinge axis and the rear hinge axis are in a plane, (v) a rear-end portion of the first leg and a front-end portion of the second leg are connected by a middle hinge, wherein the middle defines a middle-hinge axis, wherein the middle-hinge axis is on a first side of the plane if the blocking member is in the blocking position ( α = α min) and on the opposite side of the plane, if the blocking member has been shifted to the released position ( α), (vi) the front leg and the rear leg define an angle α, wherein in the blocking position α min ≤ α ≤ 180°, and in the released position α > 180°, wherein α min ∈ [90°, 180°[, α min = const.. - the latch module has a first end and a second end, wherein the first end is configured to face towards the door jamb and the second end is configured to extend into a mortise of a door, - the housing movably supports the latch bolt and the guard bolt, - the latch bolt and the guard bolt each have an extended and a retracted position and each are biased into their respective extended position, - the stem has a longitudinal axis and is movably supported relative to the housing and in that the stem has a closed position and an open position, - the stem is movably supported relative to the latch bolt, - the stem has a block configured to entrain an abutment of the latch bolt, if the stem reaches a first intermediate position while being moved from the stem's closed position towards the stem's open position, - the blocking member is movably supported between a blocking position ( α) and a released position ( α), and wherein the blocking member is configured • to block a retraction of the latch bolt, when in the blocking position and • to release blocking the retraction of the latch bolt, when the blocking member is in the released position ( α), • to block a retraction of the latch bolt, when in the blocking position and • to release blocking the retraction of the latch bolt, when the blocking member is in the released position ( α), - the guard bolt is configured to maintain the blocking member in the blocking member's released position, if the guard bolt is in the guard bolt's extended position, (i) the blocking member comprises a first leg and a second leg, (ii) a front-end portion of the first leg is connected by a front hinge to the latch bolt, wherein the front hinge defines a front hinge axis, (iii) a rear end of the second leg is connected by a rear hinge to the housing, wherein the rear hinge defines a rear hinge axis, (iv) the front hinge axis and the rear hinge axis are in a plane, (v) a rear-end portion of the first leg and a front-end portion of the second leg are connected by a middle hinge, wherein the middle defines a middle-hinge axis, wherein the middle-hinge axis is on a first side of the plane if the blocking member is in the blocking position ( α = α min) and on the opposite side of the plane, if the blocking member has been shifted to the released position ( α), (vi) the front leg and the rear leg define an angle α, wherein in the blocking position α min ≤ α ≤ 180°, and in the released position α > 180°, wherein α min ∈ [90°, 180°[, α min = const..