traits - don more than 3 pojos, got IllegalArgumentException

as the POJO I am using the Message class that comes with the project created by the Eclipse plugin. now the rule file: declare Message @Traitable end declare NiceMessage @format(trait) end rule load when then Message message = new Message(); message.setMessage("Hello World"); insert(message); don(message, NiceMessage.class); Message unreadMessage = new Message(); unreadMessage.setMessage("unread"); insert(unreadMessage); don(unreadMessage, NiceMessage.class); Message oldMessage = new Message(); oldMessage.setMessage("old"); insert(oldMessage); System.out.println("don " + oldMessage); don(oldMessage, NiceMessage.class); //<--- exception happens here System.out.println("wont reach this point"); end When I run this and rule 'load' fires the third 'don' will throw the following exception: Exception executing consequence for rule "load" in com.mycompany.app: java.lang.IllegalArgumentException: argument type mismatch at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1251) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:709) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:673) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:221) at com.mycompany.app.DroolsTest.main(DroolsTest.java:44) Caused by: java.lang.IllegalArgumentException: argument type mismatch at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:532) at org.drools.factmodel.traits.TraitFactory.getProxy(TraitFactory.java:92) at org.drools.base.DefaultKnowledgeHelper.don(DefaultKnowledgeHelper.java:502) at org.drools.base.DefaultKnowledgeHelper.don(DefaultKnowledgeHelper.java:522) at com.mycompany.app.Rule_load_86ecf966a4c14d8486844cfae2e1e0d8.defaultConsequence(Rule_load_86ecf966a4c14d8486844cfae2e1e0d8.java:21) at com.mycompany.app.Rule_load_86ecf966a4c14d8486844cfae2e1e0d8DefaultConsequenceInvokerGenerated.evaluate(Unknown Source) at com.mycompany.app.Rule_load_86ecf966a4c14d8486844cfae2e1e0d8DefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091) ... 6 more