Got an error while parsing grammar wrong argument type Class (expected Module)

[Ivan Lo]

Hi I've got an error while parsing my grammar

 TypeError:

       wrong argument type Class (expected Module)

     # (eval):311:in `extend'

     # (eval):311:in `_nt_line'

     # (eval):21:in `block in _nt_document'

     # (eval):20:in `loop'

     # (eval):20:in `_nt_document'

     # /Users/gingray/.rvm/gems/ruby-2.2.2/gems/treetop-1.6.8/lib/treetop/runtime/compiled_parser.rb:18:in `parse'

     # ./app/services/parser/chord_parser.rb:8:in `parse'

     # ./spec/services/parser/chord_parser_spec.rb:3:in `block (2 levels) in <top (required)>'

     # ./spec/services/parser/chord_parser_spec.rb:5:in `block (2 levels) in <top (required)>'

     # ./spec/spec_helper.rb:36:in `block (2 levels) in <top (required)>'

here my grammar

grammar TreetopChord

  rule document

    (line)*

  end

  rule text

    [a-zA-Z0-9,.\s]+ <TextLiteral>

  end

  rule chord

    '{' [0-9#b/]+ '}' <ChordExpression>

  end

  rule title

    '[' [a-z]+ ']' <TitleLiteral>

  end

  rule line

    (((text / chord / title ) [\r\n]+) / (text / chord / title )) <LineLiteral>

  end

end

I've got error on <LineLiteral> if i remove this everything goes fine, but I don't know why this happens also I try to use other way for grammar like

  rule line

    (text / chord / title ) [\r\n]+ <LineLiteral> / (text / chord / title ) <LineLiteral>

  end

but got the same result.

Really grateful for any kind of help. Thanks in advance.