[rules-dev] Order of retraction matters

5.3.0 Final. KnowledgeBase using STREAM, running a stateful session in one thread, inserting events from another fact. class Event{ String name; } class Monitor{ Event event; String name; } rule "start monitoring" when $e: Event($name: name) not Monitor( name == $name ) then insert( new Monitor( $e, $name ) ); end rule "timeout" timer( int: 10s ) when $m: Monitor( name == $name ) $e: Event($name: name) then retract( $m ); // ======================= retract( $m.getEvent() ); // ======================== end This order of retracts results in a NPE, see the dump below. Reversing these two works correctly. Exception in thread "main" Exception executing consequence for rule "start monitoring" in hashcode: java.lang.NullPointerException at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029) at org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1229) at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:753) at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:729) at org.drools.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:234) at hashcode.Main.execute(Main.java:148) at hashcode.Main.main(Main.java:206) Caused by: java.lang.NullPointerException at org.drools.base.hashcode.StateEvent42211789$getItemName.getValue(Unknown Source) at org.drools.base.ClassFieldReader.getValue(ClassFieldReader.java:87) at org.drools.rule.Declaration.getValue(Declaration.java:219) at hashcode.Rule_start_monitoringDefaultConsequenceInvoker.evaluate(Unknown Source) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091) ... 7 more