We are having some serious issues with some rules, they are throwing a NullPointerException and we don't understand why. I have tried to narrow down the problem to the smallest rule possible, now this rule doesn't really make much sense put like this but the real rule is more complex with more constraints. At the end the result is the same: a NPE. I have tried it with many Drools versions from 5.x to latest 6.3.0-SNAPSHOT. I tested this in isolation with the minimum amount of code possible, and attached it as well if someone wants to try it quickly. Note that if line 2 of the when: $a : Integer() is moved as first line, the rule runs ok. Please find the reproducer here: https://groups.google.com/forum/#!topic/drools-usage/-oNqu3l4cqE
Fixed by https://github.com/droolsjbpm/drools/commit/ef552a6f1
Cherry-picked to 6.2.x with https://github.com/droolsjbpm/drools/commit/eec8bfc4bf0192c66f54c28e6a2ba690b0a5fb82
Reproduced on old version. With 6.2.0.Final-redhat-2 NPE is no longer thrown. Verified
The needinfo request[s] on this closed bug have been removed as they have been unresolved for 1000 days