Bug with DataMapper 1.1.0, Ruby 1.8.6 -- undefined method 'first'

Code

# Note -- DataMapper no longer officially supports 1.8.6.
# That's why this problem happens.
# For best results, switch to Ruby >= 1.8.7.
# However, if you simply cannot upgrade, this might help.

class Banner
  include DataMapper::Resource

  property :id, Serial
  property :message_id, Integer, :required => true

  belongs_to :message
end

class Message
   include DataMapper::Resource
   property :id, Serial

   has n, :banners
end

Banner.first.message_id # works
Message.get(Banner.first.message_id) # works
Banner.first.message # generates exception below

exception_string = <<'EOS'
NoMethodError: undefined method `first' for [#<DataMapper::Property::Serial @model=Bliss::Message @name=:id>]:DataMapper::PropertySet
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/query.rb:67:in `target_conditions'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/associations/many_to_one.rb:79:in `source_scope'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/associations/relationship.rb:156:in `query_for'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/repository.rb:114:in `scope'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/associations/relationship.rb:153:in `query_for'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/associations/many_to_one.rb:97:in `resource_for'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/associations/many_to_one.rb:181:in `lazy_load'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/resource/state/persisted.rb:23:in `lazy_load'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/resource/state/persisted.rb:8:in `get'
	from /usr/lib/ruby/gems/1.8/gems/dm-core-1.1.0/lib/dm-core/model/relationship.rb:345:in `message'
	from (irb):1
EOS

monkey patch which fixes the problem

module Enumerable
  unless instance_methods.include?("first")
    def first(num = nil)
      if num == nil
        holder = nil
        catch(:got_element) do
          each do |e|
            holder = e
            throw(:got_element)
          end
        end
        holder
      else
        holder = []
        catch(:got_elements) do
          each do |e|
            holder << e
            throw(:got_element) if num == 0
            num -= 1
          end
        end
        holder
      end
    end
  end
end