A forage harvester comprising a cutting edge sharpness detection device for detecting a degree of cutting edge sharpness of a cutting assembly for the comminution of a flow of harvested material, wherein the cutting assembly has a knife drum with a plurality of chopping knives as well as at least one counter cutter which cooperates with the chopping knives to comminute the flow of harvested material, wherein the flow of harvested material is fed to the cutting assembly via a pre-pressing unit, wherein the flow of harvested material defines a material inflow zone from the pre-pressing unit to the location at which the chopping knives cooperate with the at least one counter cutter to comminute the flow of harvested material, wherein the cutting edge sharpness detection device activates at least one magnetic circuit (38, 39) by means of a system of magnets, wherein the respective magnetic circuit (38, 39) is closed via the respective chopping knife upon a rotation of the knife drum as soon as one of the chopping knives passes the system of magnets, wherein the cutting edge sharpness detection device detects the magnetic flux in the respective magnetic circuit (38, 39) and, based on a detected variation in a magnetic parameter concerning the magnetic flux, detects a reduction in the degree of cutting edge sharpness of the respective chopping knife, wherein the system of magnets is positioned outside the material inflow zone of the cutting assembly, wherein the cutting assembly has a housing drum in which the knife drum rotates wherein, following comminution by cooperation of the chopping knives and counter cutter, the flow of harvested material is conveyed away from the counter cutter between the knife drum and the housing drum, wherein the housing drum comprises a drum bottom, a drum rear and a drum back wall wherein, following its comminution, the flow of harvested material is conveyed out of the housing drum through an opening provided between the drum bottom and the drum rear into an outflow channel, characterized in that at least a portion of the magnetic flux of the magnetic circuit (38, 39) closed by means of the respective chopping knife is guided along at least a longitudinal section (L 1, L 2) of the respective chopping knife in the chopping knife, and the system of magnets is disposed on the drum bottom or on the drum rear or on the drum back wall of the housing drum. wherein the cutting assembly has a knife drum with a plurality of chopping knives as well as at least one counter cutter which cooperates with the chopping knives to comminute the flow of harvested material, wherein the flow of harvested material is fed to the cutting assembly via a pre-pressing unit, wherein the flow of harvested material defines a material inflow zone from the pre-pressing unit to the location at which the chopping knives cooperate with the at least one counter cutter to comminute the flow of harvested material, wherein the cutting edge sharpness detection device activates at least one magnetic circuit (38, 39) by means of a system of magnets, wherein the respective magnetic circuit (38, 39) is closed via the respective chopping knife upon a rotation of the knife drum as soon as one of the chopping knives passes the system of magnets, wherein the cutting edge sharpness detection device detects the magnetic flux in the respective magnetic circuit (38, 39) and, based on a detected variation in a magnetic parameter concerning the magnetic flux, detects a reduction in the degree of cutting edge sharpness of the respective chopping knife, wherein the system of magnets is positioned outside the material inflow zone of the cutting assembly, wherein the cutting assembly has a housing drum in which the knife drum rotates wherein, following comminution by cooperation of the chopping knives and counter cutter, the flow of harvested material is conveyed away from the counter cutter between the knife drum and the housing drum, wherein the housing drum comprises a drum bottom, a drum rear and a drum back wall wherein, following its comminution, the flow of harvested material is conveyed out of the housing drum through an opening provided between the drum bottom and the drum rear into an outflow channel, characterized in that at least a portion of the magnetic flux of the magnetic circuit (38, 39) closed by means of the respective chopping knife is guided along at least a longitudinal section (L 1, L 2) of the respective chopping knife in the chopping knife, and the system of magnets is disposed on the drum bottom or on the drum rear or on the drum back wall of the housing drum.