Unloader for a compressor, said unloader (1) comprising a housing (2) with an inlet (3) and an outlet (4), and whereby the unloader (1) is further provided with a piston rod (5) which is arranged moveably in a reciprocating manner in the housing (2), whereby on one end (5a) of the piston rod (5) a valve (7) is provided to be able to close the outlet (4) and whereby on the other end (5b) of the piston rod (5) a piston (8) is arranged, the piston being arranged moveably in a reciprocating manner in a thereto provided cavity (9) of the unloader (1), said cavity (9) being at least partially delimited by a lid (10) which is provided on the housing (2) and which is also part of the unloader (1), whereby sealing means (11) are provided for the leakage-free movement of the piston (8) in said cavity (9), whereby the cavity (9) in which the piston (8) is arranged moveably in a reciprocating manner is provided at least partially in the lid (10).