Dear developers, I've stumbled over another nullpointer exception when using the enabled attribute in conjunction with deleting and adding rules to the kbase. For my test I have only one simple rule rule 'newUser' enabled(!RuleEngineConf.LOAD) when $evt : EventObject(type=='new_user') from entry-point eventstream then updateApi.createPlayer($evt.getPlayerid(), true, $evt.getId()); retract($evt); Not I execute the following sequence 1. setting LOAD=false 2. insert a "new_user" event (works as expected, RHS called) 3. setting LOAD=true 4. insert another "new_user" event (works as expected, RHS NOT called) 5. setting LOAD=false 6. insert another "new_user" event (works as expected, RHS called, which ends up having two new entities in my entity provider) 7. delete the "newUser" rule; ends up with the following stacktrace java.lang.NullPointerException at org.drools.reteoo.RuleTerminalNode$RTNCleanupAdapter.cleanUp(RuleTerminalNode.java:514) at org.drools.reteoo.BetaNode.doRemove(BetaNode.java:458) at org.drools.common.BaseNode.remove(BaseNode.java:109) at org.drools.reteoo.RuleTerminalNode.doRemove(RuleTerminalNode.java:358) at org.drools.common.BaseNode.remove(BaseNode.java:109) at org.drools.reteoo.ReteooBuilder.removeRule(ReteooBuilder.java:261) at org.drools.reteoo.ReteooRuleBase.removeRule(ReteooRuleBase.java:459) at org.drools.common.AbstractRuleBase.removeRule(AbstractRuleBase.java:1107) at org.drools.common.AbstractRuleBase.removeRule(AbstractRuleBase.java:1085) at org.drools.impl.KnowledgeBaseImpl.removeRule(KnowledgeBaseImpl.java:208) 8. adding the rule again is followed by stacktrace java.lang.NullPointerException at org.drools.reteoo.ReteooBuilder.removeRule(ReteooBuilder.java:259) at org.drools.reteoo.ReteooRuleBase.removeRule(ReteooRuleBase.java:459) at org.drools.common.AbstractRuleBase.removeRule(AbstractRuleBase.java:1107) at org.drools.common.AbstractRuleBase.mergePackage(AbstractRuleBase.java:851) at org.drools.common.AbstractRuleBase.addPackages(AbstractRuleBase.java:610) at org.drools.reteoo.ReteooRuleBase.addPackages(ReteooRuleBase.java:472) at org.drools.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:150) However, when I omit step 4., i.e., leaving no orphan event in the WM, everything works fine, so obviously the ignored event is causing the exception somehow, i.e., the object retrieved from the activation is null (the clean up method seems to pickup the activation from the leftTuple which is null) Maybe I dont understand it correctly, then I would be happy if someone explains the proper usage. Thanks a lot in advance, Philipp