Hi, > In tree walker, > > ruleAlt > : > RULE_ALT graph > ; I think you have to write: ruleAlt : #(RULE_ALT graph) ; because graph is a child of RULE_ALT, not a sibling. If RULE_ALT really does not have any children, there might be an additional bug in your "graph" rule or in the tree construction. Regards, Joerg