Hi Mark, This is the gist of the IRC discussion (raised by nik9000) you was asking about. I tried with a new download from trunk and the CCE remains:- class Taggable {} class Asset extends Taggable {} class TagDataReceivedEvent { private final Taggable taggable; public Taggable getTaggable() { return taggable; } } rule "f" when $e: TagDataReceivedEvent(newLocation != oldLocation) $a: Asset() from $e.taggable then System.err.println("ASF" + $a); end ClassCastException thrown on the "from" - you thought this might have been changed to fail (I took to mean as "not match" rather than a RTE failue). Cheers, Mike