[rules-users] NullPointerException when updating a fact

Hi dear drools team, I've got a strange problem and hope someone can help me. I'm using drools 5.5.0. I have some rules to validate user input. These will set the valid flag on a fact to false and insert a Message fact into working memory that will contain a message and a reference to the causing fact. I also have a rule to retract Messages for facts which are not invalid anymore. I observe a NullPointerException originating at DefaultAgenda.createActivation() when I perform following steps: Insert a valid FirstName and call session.fireAllRules(). Change the FirstName to become invalid, call session.update() on it and call session.fireAllRules(). The rule for retracting messages is the cause for the problem. My question is, how can I fix it? Or is there a better way to manage error messages? Thank you -- View this message in context: http://drools.46999.n3.nabble.com/NullPointerException-when-updating-a-fa... Sent from the Drools: User forum mailing list archive at Nabble.com.