After upgrading the drools jars to 5.5.0 from 5.0.1 we are unable to execute the rule flows. -------------------------------------------------------------------------------------------- Key: DROOLS-147 URL: https://issues.jboss.org/browse/DROOLS-147 Project: Drools Issue Type: Component Upgrade Security Level: Public(Everyone can see) Affects Versions: 5.5.0.Final Environment: Websphere application server 6.1 Reporter: Prashant Hariharan Assignee: Mark Proctor Attachments: rfissue.zip After upgrading the drools jars to 5.5.0 from 5.0.1 we are unable to execute the rule flows. The drools engine throws a null pointer exception the stackrace of which is as follows : The stacktrace of the same can be seen below: Exception executing consequence for rule "Initialisation For All" in com.mastek.groupelixir.schemeuw.rules.controller: java.lang.NullPointerException at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1297) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1221) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1456) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:710) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:684) at org.drools.reteoo.ReteooStatelessSession.execute(ReteooStatelessSession.java:206) After some detailed analysis the problem seems to be with the usage of Rule base,PacakgeBuilder and StatlessSessions as opposed to the set of KnowledgeBaes,KowledgeBuilders and StatelessKnowledgeSessions for executing the rule flows. The rule flow,drl and the standalone program has been attached for reference. The problem is that the application still uses the packagebuilder and it will be difficult to upgrade it to knowledge builders So is there any workaround for the same?