A mortice lock (1) with a housing (2) having a non-circular opening (13) and a latch bolt (3) with a longitudinal axis (9). The latch bolt (3) has a main portion (10) received in the non-circular opening (13) to prevent the latch bolt (3) from turning around its longitudinal axis (9). The lock (1) further comprises a guiding mechanism which enables pushing the latch bolt (3) inside the lock (1) into a position in which the main portion (10) is disengaged from the non-circular opening (13) and the latch bolt (3) can be reversed easily between a left-handed and a right-handed position without having to remove a front wall of the housing (2) and without having to release the latch bolt (3) to remove it from the lock (1).