Hello, I have a scenario where I have a rule that is searching for a particular object inside a list and the list is an entry in a hashmap. An example of the class structure looks something like this. class Player { String name; } class TeamRoster { // Maps team name to players Map<String, List<Player>> teams; } The goal of the rule is to activate when there is a player named John on the Dodgers team. I have tried writing rules a couple of ways but end up with errors using either approach. My first approach was the following: dialect "mvel" rule when $roster : TeamRoster() $player : Player(name == "John") from $roster.teams["Dodgers"] then ... end However this resulted in the following error: Unable to Analyse Expression $roster.teams["Dodgers"]: sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl cannot be cast to java.lang.Class] So I tried changing it up with the following... dialect "mvel" rule when $roster : TeamRoster() $player : Player(name == "John") eval($roster.teams["Dodgers"] contains $player then ... end This effectively yields the same error: Expression $roster.teams["Dodgers"] contains $player: sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl cannot be cast to java.lang.Class] Note I am using Drools 6.0.1.Final. Is this some sort bug or limitation with the rules parser? Assuming I cannot change the class structure how can I achieve what I need? Thanks in advance, Jean-Philippe Steinmetz