Looking at WorkItemHandlerOption implements MultiValueKnowledgeSessionOption contains public static final String PROPERTY_NAME = "drools.workItemHandlers"; which is used as public String getPropertyName() { return PROPERTY_NAME+name; } so that some actual property setting would have to be the ugly concatenation drools.workItemHandlerstheName = theHandler All (!) other multi-valued options use a period to separate the fixed part from the user-defined tag, i.e., public static final String PROPERTY_NAME = "drools.workItemHandlers."; -W