A knife assembly comprising: a knife blade (101, 200) of which a front edge is a cutting edge, the knife blade (101, 200) being a corrugated knife blade (101, 200) comprising a corrugated part having a continuous shape defining a periodic pattern of peaks and valleys over a certain distance; a holder (100, 201) configured for supporting the knife blade (101, 200); a clamp (102, 202, 650, 700) arranged for clamping the knife blade (101, 200) onto the holder (100, 201); and a fastening mechanism (103, 203) cooperating with the holder (100, 201) and clamp (102, 202, 650, 700) for securing and clamping the knife blade (101, 200) to a clamped state in which it is clamped between the clamp (102, 202) and the holder (100, 201, 650, 700) with the cutting edge protruding at a front side of the knife assembly; the clamp (102, 202, 650, 700) having first clamping portions which are arranged along a first clamping line (120, 220) at a front side of the clamp and are provided for in the clamped state contacting the knife blade (101, 200) at a complementary contact line on the knife blade (101, 200) rearward from the front edge of the knife blade; characterised in that the clamp (102, 202, 650, 700) has an inwardly corrugated shape complementary to that of the knife blade (101, 200) and comprises second clamping portions (115, 215, 665, 715), formed by inwardly bevelled parts of the clamp with a shape corresponding to complementary contact surfaces of the knife blade (101, 200), the second clamping portions (115, 215, 665, 715) being positioned in a second clamping region which extends up to a distance rearward from said first clamping line (120, 220) and being provided for in the clamped state contacting the knife blade at the complementary contact surfaces, such that in the clamped state the clamp (102, 202, 650, 700) contacts the knife blade (101, 200) with the first clamping portions and the second clamping portions (115, 215, 665, 715) which together provide a contact over a width of the knife blade. a knife blade (101, 200) of which a front edge is a cutting edge, the knife blade (101, 200) being a corrugated knife blade (101, 200) comprising a corrugated part having a continuous shape defining a periodic pattern of peaks and valleys over a certain distance; a holder (100, 201) configured for supporting the knife blade (101, 200); a clamp (102, 202, 650, 700) arranged for clamping the knife blade (101, 200) onto the holder (100, 201); and a fastening mechanism (103, 203) cooperating with the holder (100, 201) and clamp (102, 202, 650, 700) for securing and clamping the knife blade (101, 200) to a clamped state in which it is clamped between the clamp (102, 202) and the holder (100, 201, 650, 700) with the cutting edge protruding at a front side of the knife assembly; the clamp (102, 202, 650, 700) having first clamping portions which are arranged along a first clamping line (120, 220) at a front side of the clamp and are provided for in the clamped state contacting the knife blade (101, 200) at a complementary contact line on the knife blade (101, 200) rearward from the front edge of the knife blade; characterised in that the clamp (102, 202, 650, 700) has an inwardly corrugated shape complementary to that of the knife blade (101, 200) and comprises second clamping portions (115, 215, 665, 715), formed by inwardly bevelled parts of the clamp with a shape corresponding to complementary contact surfaces of the knife blade (101, 200), the second clamping portions (115, 215, 665, 715) being positioned in a second clamping region which extends up to a distance rearward from said first clamping line (120, 220) and being provided for in the clamped state contacting the knife blade at the complementary contact surfaces, such that in the clamped state the clamp (102, 202, 650, 700) contacts the knife blade (101, 200) with the first clamping portions and the second clamping portions (115, 215, 665, 715) which together provide a contact over a width of the knife blade.