[rules-users] Throws NPE when comparing one property to another of the same bean class

That's almost all the details in the mail subject; When I am running this rule in drools 5.1.0: package com.sample import com.sample.Msg; import java.util.Date; rule "Hello World" when m1:Msg() m:Msg(dbl > lo || m1.in == in) then end The java bean named 'Msg' definition: package com.sample; import java.util.Date; import java.util.HashSet; import java.util.Set; public class Msg { private Long lo = 5l; private double dbl = 5.5; private Date date = new Date(); private int in = 4; private boolean bool; private Set<String> set = new HashSet<String>(); ... // getter and setters ignored then it throws exception : java.lang.NullPointerException at org.drools.reteoo.LeftTuple.get(LeftTuple.java:399) at org.drools.reteoo.LeftTuple.get(LeftTuple.java:434) at org.drools.rule.VariableRestriction$DoubleVariableContextEntry.updateFromTuple(VariableRestriction.java:563) at org.drools.rule.AbstractCompositeConstraint$MultiFieldConstraintContextEntry.updateFromTuple(AbstractCompositeConstraint.java:306) at org.drools.common.SingleBetaConstraints.updateFromTuple(SingleBetaConstraints.java:123) at org.drools.reteoo.JoinNode.assertLeftTuple(JoinNode.java:77) at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:189) at org.drools.reteoo.SingleLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:138) at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:148) at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:450) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:378) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:190) at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:145) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1174) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1123) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:917) at org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:251) at com.sample.DroolsTest.main(DroolsTest.java:43) I think I am doing nothing wrong with the code, is this a bug or something? Or just comparing properties in the same bean class is illegal?