Good catch, it is indeed a 5.6 regression. Fixed, the pull request should be merged momentarily. Davide -- View this message in context: http://drools.46999.n3.nabble.com/rules-users-session-deserialization-slidingTimeWindow-NPE-tp4026400p4026411.html Sent from the Drools: User forum mailing list archive at Nabble.com.