NoMethodError while executing app.rb in ruby -

NoMethodError while executing app.rb in ruby -

when seek run programme in rubymine got nomethoderror.

there description of error:

/users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:166:in `<module:classmethods>': undefined method `inherited_instance_variables' sequel::plugins:module (nomethoderror) /users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:166:in `<module:classmethods>': undefined method `inherited_instance_variables' sequel::plugins:module (nomethoderror) /users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:136:in `<module:jsonserializer>' /users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:111:in `<module:plugins>' /users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:4:in `<module:sequel>' /users/admin/.rvm/gems/ruby-2.1.2@global/gems/sequel-4.11.0/lib/sequel/plugins/json_serializer.rb:3:in `<top (required)>' /users/admin/documents/projects/marsu-schedule-server/json_generator/json_generator.rb:4:in `require' /users/admin/documents/projects/marsu-schedule-server/json_generator/json_generator.rb:4:in `<top (required)>' /users/admin/documents/projects/marsu-schedule-server/msu_server.rb:10:in `require' /users/admin/documents/projects/marsu-schedule-server/msu_server.rb:10:in `<top (required)>' /users/admin/documents/projects/marsu-schedule-server/app.rb:5:in `require' /users/admin/documents/projects/marsu-schedule-server/app.rb:5:in `<top (required)>' -e:1:in `load' -e:1:in `<main>'

executing in terminal (mac os x) gives same error.

thanks in advance!

ruby-on-rails ruby osx sequel nomethoderror