An arrangement and a method for controlling a shutdown phase of a WHR-system. The WHR system includes a main circuit (4) which includes a pump (3), an evaporator (5), an expander (7) and a condenser (10), and a compensation tank (12) which is configured to compensate for volume changes of a working fluid in the main circuit (4) during operation of the WHR system. The arrangement includes a control unit (26) configured to receive information when the shutdown phase of the WHR system is to be initiated and a flow device able to supply working fluid from the compensation tank (12) to the main circuit (4). The control unit (26) is configured to activate the flow device such that working fluid is supplied from the compensation tank (12) to the main circuit (4) when it receives information indication that the shutdown phase of the WHR system is to be initiated.