The invention concerns a displacer unit (3) of a Stirling cooling arrangement (1) with a housing (20), a displacer (10) that is arranged to reciprocate in a cylinder (11) between a cold side (12) and a hot side (13) of the displacer unit (3), and a regenerator (16) arranged between the cold side (12) and the hot side (13), a gas being permitted to flow through said regenerator (16) on its way from the cold side (12) to the hot side (13) and back. It is endeavoured to permit defrosting in a simple manner. For this purpose, at least one bypass conduit (23) is arranged in parallel to the regenerator (16), an opening or closing of said bypass conduit (23) being con- trolled by a control unit (22).