Serializes numbers with more than 53 bit as strings.

fixnum_serialization.rb

class Fixnum
  alias_method :default_as_json, :as_json

  # Serializes long integers as strings.
  def as_json(options = {})
    if self.bit_length > 53
      "#{ default_as_json(options) }"
    else
      default_as_json(options)
    end
  end

  def to_json(options = {})
    as_json(options)
  end
end