Datamapper DataMapper → 1.0.0

I just tried running specs for my new DataMapper plugin (http://github.com/postmodern/dm-is-read_only) using the spec/spec_helper.rb from dm-migrations. Under Ruby 1.9.1 I get a trivial NoMethodError:

/home/hal/.bundle/ruby/1.9.1/bundler/gems/dm-core-37b4bd22b9e3842977cf83d32baba459607e900a-master/lib/dm-core/spec/lib/adapter_helpers.rb:71:in `setup_adapters': undefined method `only' for #<Hash:0x00000001d9eff0> (NoMethodError)
    from /vault/1/code/dm-is-read_only/spec/spec_helper.rb:29:in `<top (required)>'
    from /vault/1/code/dm-is-read_only/spec/integration/read_only_spec.rb:1:in `require'
    from /vault/1/code/dm-is-read_only/spec/integration/read_only_spec.rb:1:in `<top (required)>'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/example_group_runner.rb:15:in `load'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/example_group_runner.rb:15:in `block in load_files'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/example_group_runner.rb:14:in `each'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/example_group_runner.rb:14:in `load_files'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/options.rb:133:in `run_examples'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/lib/spec/runner/command_line.rb:9:in `run'
    from /usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/bin/spec:5:in `<main>'
rake aborted!
Command /usr/bin/ruby19 -I"lib:lib:spec"  "/usr/lib/ruby19/gems/1.9.1/gems/rspec-1.3.0/bin/spec" "spec/integration/read_only_spec.rb" --options .specopts failed

Gemfile:

source 'http://rubygems.org'
datamapper = 'git://github.com/datamapper'

group :runtime do
  if ENV['EXTLIB']
    gem 'extlib', '~> 0.9.15', :git => "#{datamapper}/extlib.git"
  else
    gem 'activesupport', '~> 3.0.0.beta3', :git => 'git://github.com/rails/rails.git', :require => nil
  end

  gem 'dm-core',    '~> 0.10.3', :git => "#{datamapper}/dm-core.git"
end

group :development do
  gem 'rake',       '~> 0.8.7'
  gem 'jeweler',    '~> 1.4.0', :git => 'git://github.com/technicalpickles/jeweler.git'
  gem 'yard',       '~> 0.5.3'
end

group :test do
  gem 'data_objects',   '~> 0.10.2', :git => "#{datamapper}/do.git"
  gem 'do_sqlite3', '~> 0.10.2', :git => "#{datamapper}/do.git"

  if ENV['ADAPTERS']
    adapters = ENV['ADAPTERS'].split(/\s+/).map { |name|
      name.downcase
    }.uniq

    adapters.each do |name|
      gem "dm-adapter-#{name}",   '~> 0.10.3', :git => "#{datamapper}/dm-adapter-#{name}.git"
    end
  end
end

gem 'rspec',    '~> 1.3.0', :group => [:development, :test]