[GrammarKit] Store parsed token in Psi class

I have the following rule:

Def ::= ('val' | 'var') PatternDef

class which represents 'Def' rule doesn't contain tokens, it contains only PatternDef reference.
Is there a way to make GrammarKit generator to store which token ('var' or 'val') was matched?
Right now I have to do this:

Def ::= 'val' ValDef | 'var' VarDef

Thanks.