The use of assistive robots in domestic environments can raise significant ethical concerns, from the risk of individual ethical harm to wider societal ethical impacts including culture flattening and compromise of human dignity. It is therefore essential to ensure that technological development of these robots is informed by robust and inclusive techniques for mitigating ethical concerns. This paper presents EHAZOP, a method for conducting an ethical hazard analysis on an assistive robot. EHAZOP draws upon collaborative, creative and structured processes originating within safety engineering, using these to identify ethical concerns associated with the operation of a given assistive robot. We present the results of a proof of concept study of EHAZOP, demonstrating the potential for this process to identify diverse ethical hazards in these systems.