As a workaround, you can try using FunctionName.functionName when you invoke the function, instead of just functionName. I've also tried adding: import function <package>.FunctionName.functionName; to the rule file, even when rule & function are in the same package. It seems to help in some cases but not all, for reasons I don't understand yet. -- View this message in context: http://drools.46999.n3.nabble.com/Drools-cannot-resolve-functions-even-wh... Sent from the Drools: User forum mailing list archive at Nabble.com.