diff --git a/lib/ransack.rb b/lib/ransack.rb
index 6e2e84846..53268ae21 100644
--- a/lib/ransack.rb
+++ b/lib/ransack.rb
@@ -1,6 +1,7 @@
 require 'active_support/core_ext'
 require 'ransack/configuration'
 require 'ransack/adapters'
+require 'polyamorous'
 
 Ransack::Adapters.object_mapper.require_constants
 
diff --git a/lib/polyamorous.rb b/polyamorous/lib/polyamorous.rb
similarity index 100%
rename from lib/polyamorous.rb
rename to polyamorous/lib/polyamorous.rb
diff --git a/lib/polyamorous/activerecord_5.0_ruby_2/join_association.rb b/polyamorous/lib/polyamorous/activerecord_5.0_ruby_2/join_association.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.0_ruby_2/join_association.rb
rename to polyamorous/lib/polyamorous/activerecord_5.0_ruby_2/join_association.rb
diff --git a/lib/polyamorous/activerecord_5.0_ruby_2/join_dependency.rb b/polyamorous/lib/polyamorous/activerecord_5.0_ruby_2/join_dependency.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.0_ruby_2/join_dependency.rb
rename to polyamorous/lib/polyamorous/activerecord_5.0_ruby_2/join_dependency.rb
diff --git a/lib/polyamorous/activerecord_5.1_ruby_2/join_association.rb b/polyamorous/lib/polyamorous/activerecord_5.1_ruby_2/join_association.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.1_ruby_2/join_association.rb
rename to polyamorous/lib/polyamorous/activerecord_5.1_ruby_2/join_association.rb
diff --git a/lib/polyamorous/activerecord_5.1_ruby_2/join_dependency.rb b/polyamorous/lib/polyamorous/activerecord_5.1_ruby_2/join_dependency.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.1_ruby_2/join_dependency.rb
rename to polyamorous/lib/polyamorous/activerecord_5.1_ruby_2/join_dependency.rb
diff --git a/lib/polyamorous/activerecord_5.2.0_ruby_2/join_association.rb b/polyamorous/lib/polyamorous/activerecord_5.2.0_ruby_2/join_association.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.2.0_ruby_2/join_association.rb
rename to polyamorous/lib/polyamorous/activerecord_5.2.0_ruby_2/join_association.rb
diff --git a/lib/polyamorous/activerecord_5.2.0_ruby_2/join_dependency.rb b/polyamorous/lib/polyamorous/activerecord_5.2.0_ruby_2/join_dependency.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.2.0_ruby_2/join_dependency.rb
rename to polyamorous/lib/polyamorous/activerecord_5.2.0_ruby_2/join_dependency.rb
diff --git a/lib/polyamorous/activerecord_5.2.1_ruby_2/join_association.rb b/polyamorous/lib/polyamorous/activerecord_5.2.1_ruby_2/join_association.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.2.1_ruby_2/join_association.rb
rename to polyamorous/lib/polyamorous/activerecord_5.2.1_ruby_2/join_association.rb
diff --git a/lib/polyamorous/activerecord_5.2.1_ruby_2/join_dependency.rb b/polyamorous/lib/polyamorous/activerecord_5.2.1_ruby_2/join_dependency.rb
similarity index 100%
rename from lib/polyamorous/activerecord_5.2.1_ruby_2/join_dependency.rb
rename to polyamorous/lib/polyamorous/activerecord_5.2.1_ruby_2/join_dependency.rb
diff --git a/lib/polyamorous/join.rb b/polyamorous/lib/polyamorous/join.rb
similarity index 100%
rename from lib/polyamorous/join.rb
rename to polyamorous/lib/polyamorous/join.rb
diff --git a/lib/polyamorous/swapping_reflection_class.rb b/polyamorous/lib/polyamorous/swapping_reflection_class.rb
similarity index 100%
rename from lib/polyamorous/swapping_reflection_class.rb
rename to polyamorous/lib/polyamorous/swapping_reflection_class.rb
diff --git a/lib/polyamorous/tree_node.rb b/polyamorous/lib/polyamorous/tree_node.rb
similarity index 100%
rename from lib/polyamorous/tree_node.rb
rename to polyamorous/lib/polyamorous/tree_node.rb
diff --git a/polyamorous/lib/polyamorous/version.rb b/polyamorous/lib/polyamorous/version.rb
new file mode 100644
index 000000000..c480c5bbf
--- /dev/null
+++ b/polyamorous/lib/polyamorous/version.rb
@@ -0,0 +1,3 @@
+module Polyamorous
+  VERSION = '2.1.1'
+end
diff --git a/polyamorous/polyamorous.gemspec b/polyamorous/polyamorous.gemspec
new file mode 100644
index 000000000..d6318b831
--- /dev/null
+++ b/polyamorous/polyamorous.gemspec
@@ -0,0 +1,37 @@
+# -*- encoding: utf-8 -*-
+$:.push File.expand_path("../lib", __FILE__)
+require "polyamorous/version"
+
+Gem::Specification.new do |s|
+  s.name        = "polyamorous"
+  s.version     = Polyamorous::VERSION
+  s.authors     = ["Ernie Miller", "Ryan Bigg", "Jon Atack", "Xiang Li"]
+  s.email       = ["ernie@erniemiller.org", "radarlistener@gmail.com", "jonnyatack@gmail.com", "bigxiang@gmail.com"]
+  s.homepage    = "https://github.com/activerecord-hackery/ransack/tree/master/polyamorous"
+  s.license     = "MIT"
+  s.summary     = %q{
+    Loves/is loved by polymorphic belongs_to associations, Ransack, Squeel, MetaSearch...
+  }
+  s.description = %q{
+    This is just an extraction from Ransack/Squeel. You probably don't want to use this
+    directly. It extends ActiveRecord's associations to support polymorphic belongs_to
+    associations.
+  }
+
+  s.rubyforge_project = "polyamorous"
+
+  s.add_dependency 'activerecord', '>= 5.0'
+  s.add_development_dependency 'rspec', '~> 3'
+  s.add_development_dependency 'machinist', '~> 1.0.6'
+  s.add_development_dependency 'faker', '~> 1.6.5'
+  s.add_development_dependency 'sqlite3', '~> 1.3.3'
+
+  s.files         = `git ls-files`.split("\n")
+  s.test_files    = `git ls-files -- {test,spec,features}/*`.split("\n")
+  s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
+  s.require_paths = ["lib"]
+
+  # specify any dependencies here; for example:
+  # s.add_development_dependency "rspec"
+  # s.add_runtime_dependency "rest-client"
+end
diff --git a/polyamorous/spec/blueprints/articles.rb b/polyamorous/spec/blueprints/articles.rb
new file mode 100644
index 000000000..42e2f14be
--- /dev/null
+++ b/polyamorous/spec/blueprints/articles.rb
@@ -0,0 +1,5 @@
+Article.blueprint do
+  person
+  title
+  body
+end
\ No newline at end of file
diff --git a/polyamorous/spec/blueprints/comments.rb b/polyamorous/spec/blueprints/comments.rb
new file mode 100644
index 000000000..1ecc7eb69
--- /dev/null
+++ b/polyamorous/spec/blueprints/comments.rb
@@ -0,0 +1,5 @@
+Comment.blueprint do
+  article
+  person
+  body
+end
\ No newline at end of file
diff --git a/polyamorous/spec/blueprints/notes.rb b/polyamorous/spec/blueprints/notes.rb
new file mode 100644
index 000000000..f1431145a
--- /dev/null
+++ b/polyamorous/spec/blueprints/notes.rb
@@ -0,0 +1,3 @@
+Note.blueprint do
+  note
+end
\ No newline at end of file
diff --git a/polyamorous/spec/blueprints/people.rb b/polyamorous/spec/blueprints/people.rb
new file mode 100644
index 000000000..b7ba882cb
--- /dev/null
+++ b/polyamorous/spec/blueprints/people.rb
@@ -0,0 +1,4 @@
+Person.blueprint do
+  name
+  salary
+end
\ No newline at end of file
diff --git a/polyamorous/spec/blueprints/tags.rb b/polyamorous/spec/blueprints/tags.rb
new file mode 100644
index 000000000..f0fb3d869
--- /dev/null
+++ b/polyamorous/spec/blueprints/tags.rb
@@ -0,0 +1,3 @@
+Tag.blueprint do
+  name    { Sham.tag_name }
+end
\ No newline at end of file
diff --git a/polyamorous/spec/helpers/polyamorous_helper.rb b/polyamorous/spec/helpers/polyamorous_helper.rb
new file mode 100644
index 000000000..8dff2699b
--- /dev/null
+++ b/polyamorous/spec/helpers/polyamorous_helper.rb
@@ -0,0 +1,26 @@
+module PolyamorousHelper
+  if ActiveRecord::VERSION::STRING >= "4.1"
+    def new_join_association(reflection, children, klass)
+      Polyamorous::JoinAssociation.new reflection, children, klass
+    end
+  else
+    def new_join_association(reflection, join_dependency, parent, klass)
+      Polyamorous::JoinAssociation.new reflection, join_dependency, parent, klass
+    end
+  end
+
+  if ActiveRecord::VERSION::STRING >= "5.2"
+    def new_join_dependency(klass, associations = {})
+      alias_tracker = ::ActiveRecord::Associations::AliasTracker.create(klass.connection, klass.table_name, [])
+      Polyamorous::JoinDependency.new klass, klass.arel_table, associations, alias_tracker
+    end
+  else
+    def new_join_dependency(klass, associations = {})
+      Polyamorous::JoinDependency.new klass, associations, []
+    end
+  end
+
+  def new_join(name, type = Polyamorous::InnerJoin, klass = nil)
+    Polyamorous::Join.new name, type, klass
+  end
+end
diff --git a/polyamorous/spec/polyamorous/join_association_spec.rb b/polyamorous/spec/polyamorous/join_association_spec.rb
new file mode 100644
index 000000000..bf843e360
--- /dev/null
+++ b/polyamorous/spec/polyamorous/join_association_spec.rb
@@ -0,0 +1,29 @@
+require 'spec_helper'
+
+module Polyamorous
+  describe JoinAssociation do
+
+    join_base, join_association_args, polymorphic = [:join_root, 'parent.children', 'reflection.options[:polymorphic]']
+    let(:join_dependency) { new_join_dependency Note, {} }
+    let(:reflection) { Note.reflect_on_association(:notable) }
+    let(:parent) { join_dependency.send(join_base) }
+    let(:join_association) {
+      eval("new_join_association(reflection, #{join_association_args}, Article)")
+    }
+
+    it 'leaves the orginal reflection intact for thread safety' do
+      reflection.instance_variable_set(:@klass, Article)
+      join_association
+      .swapping_reflection_klass(reflection, Person) do |new_reflection|
+        expect(new_reflection.options).not_to equal reflection.options
+        expect(new_reflection.options).not_to have_key(:polymorphic)
+        expect(new_reflection.klass).to eq(Person)
+        expect(reflection.klass).to eq(Article)
+      end
+    end
+
+    it 'sets the polymorphic option to true after initializing' do
+      expect(join_association.instance_eval(polymorphic)).to be true
+    end
+  end
+end
diff --git a/polyamorous/spec/polyamorous/join_dependency_spec.rb b/polyamorous/spec/polyamorous/join_dependency_spec.rb
new file mode 100644
index 000000000..dd64dc999
--- /dev/null
+++ b/polyamorous/spec/polyamorous/join_dependency_spec.rb
@@ -0,0 +1,93 @@
+require 'spec_helper'
+
+module Polyamorous
+  describe JoinDependency do
+
+    method, join_associations, join_base =
+      if ActiveRecord::VERSION::STRING >= '4.1'
+        [:instance_eval, 'join_root.drop(1)', :join_root]
+      else
+        [:send, 'join_associations', :join_base]
+      end
+
+    context 'with symbol joins' do
+      subject { new_join_dependency Person, articles: :comments }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq(2) }
+      specify { expect(subject.send(method, join_associations).map(&:join_type))
+        .to be_all { Polyamorous::InnerJoin } }
+    end
+
+    context 'with has_many :through association' do
+      subject { new_join_dependency Person, :authored_article_comments }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq 1 }
+      specify { expect(subject.send(method, join_associations).first.table_name)
+        .to eq 'comments' }
+    end
+
+    context 'with outer join' do
+      subject { new_join_dependency Person, new_join(:articles, :outer) }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq 1 }
+      specify { expect(subject.send(method, join_associations).first.join_type)
+        .to eq Polyamorous::OuterJoin }
+    end
+
+    context 'with nested outer joins' do
+      subject { new_join_dependency Person,
+        new_join(:articles, :outer) => new_join(:comments, :outer) }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq 2 }
+      specify { expect(subject.send(method, join_associations).map(&:join_type))
+        .to eq [Polyamorous::OuterJoin, Polyamorous::OuterJoin] }
+      specify { expect(subject.send(method, join_associations).map(&:join_type))
+        .to be_all { Polyamorous::OuterJoin } }
+    end
+
+    context 'with polymorphic belongs_to join' do
+      subject { new_join_dependency Note, new_join(:notable, :inner, Person) }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq 1 }
+      specify { expect(subject.send(method, join_associations).first.join_type)
+        .to eq Polyamorous::InnerJoin }
+      specify { expect(subject.send(method, join_associations).first.table_name)
+        .to eq 'people' }
+    end
+
+    context 'with polymorphic belongs_to join and nested symbol join' do
+      subject { new_join_dependency Note,
+        new_join(:notable, :inner, Person) => :comments }
+
+      specify { expect(subject.send(method, join_associations).size)
+        .to eq 2 }
+      specify { expect(subject.send(method, join_associations).map(&:join_type))
+        .to be_all { Polyamorous::InnerJoin } }
+      specify { expect(subject.send(method, join_associations).first.table_name)
+        .to eq 'people' }
+      specify { expect(subject.send(method, join_associations)[1].table_name)
+        .to eq 'comments' }
+    end
+
+    context '#left_outer_join in Rails 5 overrides join type specified',
+            if: ActiveRecord::VERSION::MAJOR >= 5 && ActiveRecord::VERSION::MINOR < 2 do
+
+      let(:join_type_class) do
+        new_join_dependency(
+          Person,
+          new_join(:articles)
+        ).join_constraints(
+          [],
+          Arel::Nodes::OuterJoin
+        ).first.joins.map(&:class)
+      end
+
+      specify { expect(join_type_class).to eq [Arel::Nodes::OuterJoin] }
+    end
+  end
+end
diff --git a/polyamorous/spec/polyamorous/join_spec.rb b/polyamorous/spec/polyamorous/join_spec.rb
new file mode 100644
index 000000000..5e2bfc3ec
--- /dev/null
+++ b/polyamorous/spec/polyamorous/join_spec.rb
@@ -0,0 +1,19 @@
+require 'spec_helper'
+
+module Polyamorous
+  describe Join do
+    it 'is a tree node' do
+      join = new_join(:articles, :outer)
+      expect(join).to be_kind_of(TreeNode)
+    end
+
+    it 'can be added to a tree' do
+      join = new_join(:articles, :outer)
+
+      tree_hash = {}
+      join.add_to_tree(tree_hash)
+
+      expect(tree_hash[join]).to be {}
+    end
+  end
+end
diff --git a/polyamorous/spec/spec_helper.rb b/polyamorous/spec/spec_helper.rb
new file mode 100644
index 000000000..21450e3ba
--- /dev/null
+++ b/polyamorous/spec/spec_helper.rb
@@ -0,0 +1,43 @@
+require 'machinist/active_record'
+require 'sham'
+require 'faker'
+require 'polyamorous'
+
+Time.zone = 'Eastern Time (US & Canada)'
+
+Dir[File.expand_path('../{helpers,support,blueprints}/**/*.rb', __FILE__)]
+.each do |f|
+  require f
+end
+
+Sham.define do
+  name     { Faker::Name.name }
+  title    { Faker::Lorem.sentence }
+  body     { Faker::Lorem.paragraph }
+  salary   { |index| 30000 + (index * 1000) }
+  tag_name { Faker::Lorem.words(3).join(' ') }
+  note     { Faker::Lorem.words(7).join(' ') }
+end
+
+RSpec.configure do |config|
+  config.before(:suite) do
+    message = "Running Polyamorous specs with #{
+      ActiveRecord::Base.connection.adapter_name
+      }, Active Record #{::ActiveRecord::VERSION::STRING}, Arel #{Arel::VERSION
+      } and Ruby #{RUBY_VERSION}"
+    line = '=' * message.length
+    puts line, message, line
+    Schema.create
+  end
+  config.before(:all)   { Sham.reset(:before_all) }
+  config.before(:each)  { Sham.reset(:before_each) }
+
+  config.include PolyamorousHelper
+end
+
+RSpec::Matchers.define :be_like do |expected|
+  match do |actual|
+    actual.gsub(/^\s+|\s+$/, '').gsub(/\s+/, ' ').strip ==
+      expected.gsub(/^\s+|\s+$/, '').gsub(/\s+/, ' ').strip
+  end
+end
diff --git a/polyamorous/spec/support/schema.rb b/polyamorous/spec/support/schema.rb
new file mode 100644
index 000000000..96994e2d4
--- /dev/null
+++ b/polyamorous/spec/support/schema.rb
@@ -0,0 +1,98 @@
+require 'active_record'
+
+ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
+
+class Person < ActiveRecord::Base
+  belongs_to :parent, class_name: 'Person', foreign_key: :parent_id
+  has_many   :children, class_name: 'Person', foreign_key: :parent_id
+  has_many   :articles
+  has_many   :comments
+  has_many   :authored_article_comments, through: :articles,
+             foreign_key: :person_id, source: :comments
+  has_many   :notes, as: :notable
+end
+
+class Article < ActiveRecord::Base
+  belongs_to              :person
+  has_many                :comments
+  has_and_belongs_to_many :tags
+  has_many   :notes, as:  :notable
+end
+
+class Comment < ActiveRecord::Base
+  belongs_to :article
+  belongs_to :person
+end
+
+class Tag < ActiveRecord::Base
+  has_and_belongs_to_many :articles
+end
+
+class Note < ActiveRecord::Base
+  belongs_to :notable, polymorphic: true
+end
+
+module Schema
+  def self.create
+    ActiveRecord::Migration.verbose = false
+
+    ActiveRecord::Schema.define do
+      create_table :people, force: true do |t|
+        t.integer  :parent_id
+        t.string   :name
+        t.integer  :salary
+        t.boolean  :awesome, default: false
+        t.timestamps null: false
+      end
+
+      create_table :articles, force: true do |t|
+        t.integer :person_id
+        t.string  :title
+        t.text    :body
+      end
+
+      create_table :comments, force: true do |t|
+        t.integer :article_id
+        t.integer :person_id
+        t.text    :body
+      end
+
+      create_table :tags, force: true do |t|
+        t.string :name
+      end
+
+      create_table :articles_tags, force: true, id: false do |t|
+        t.integer :article_id
+        t.integer :tag_id
+      end
+
+      create_table :notes, force: true do |t|
+        t.integer :notable_id
+        t.string  :notable_type
+        t.string  :note
+      end
+    end
+
+    10.times do
+      person = Person.make
+      Note.make(notable: person)
+      3.times do
+        article = Article.make(person: person)
+        3.times do
+          article.tags = [Tag.make, Tag.make, Tag.make]
+        end
+        Note.make(notable: article)
+        10.times do
+          Comment.make(article: article)
+        end
+      end
+      2.times do
+        Comment.make(person: person)
+      end
+    end
+
+    Comment.make(
+      body: 'First post!', article: Article.make(title: 'Hello, world!')
+    )
+  end
+end
diff --git a/ransack.gemspec b/ransack.gemspec
index b65668e1b..9d2e4d609 100644
--- a/ransack.gemspec
+++ b/ransack.gemspec
@@ -20,6 +20,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'activerecord', '>= 5.0'
   s.add_dependency 'activesupport', '>= 5.0'
   s.add_dependency 'i18n'
+  s.add_dependency 'polyamorous', Ransack::VERSION.to_s
   s.add_development_dependency 'rspec', '~> 3'
   s.add_development_dependency 'machinist', '~> 1.0.6'
   s.add_development_dependency 'faker', '~> 0.9.5'