ArgumentError - wrong number of arguments (2 for 1)

ArgumentError - wrong number of arguments (2 for 1):
  (gem) dickens-0.2.1/lib/dickens.rb:23:in `try'
  (gem) activemodel-3.2.11/lib/active_model/serializers/json.rb:91:in `as_json'
  /home/ctslin/.bundler/ruby/1.9.1/tire-22bb1c763eae/lib/tire/results/collection.rb:65:in `block in as_json'
  /home/ctslin/.bundler/ruby/1.9.1/tire-22bb1c763eae/lib/tire/results/collection.rb:65:in `map'
  /home/ctslin/.bundler/ruby/1.9.1/tire-22bb1c763eae/lib/tire/results/collection.rb:65:in `as_json'