It looks like the value objects of the accumulate framework are always Long's - even when they are Integers? Caused by: java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer at org.drools.base.accumulators.SumIntegerAccumulateFunction.accumulate(SumIntegerAccumulateFunction.java:36) at org.drools.base.accumulators.JavaAccumulatorFunctionExecutor.accumulate(JavaAccumulatorFunctionExecutor.java:79) Here's the piece of code: public void accumulate(Object context, Object value) { SumIntegerAccumulateFunction.SumData data = (SumIntegerAccumulateFunction.SumData) context; data.total += ((Integer) value).intValue(); // breaks } Here's the drl: when $totalDistance : Integer() from accumulate( Hop($distance : distance), sumInteger($distance) ); Here's the Hop object: public int getDistance() { ... } Look ma, no longs :) Still a ClassCastException on them though. I must be missing something really obvious? -- With kind regards, Geoffrey De Smet