diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index e3d8356f49b..cd366ac8b72 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -109,7 +109,7 @@ module ActiveRecord
         case associations
         when Symbol, String
           reflection = parent.reflections[associations.to_s.intern] or
-          raise ConfigurationError, "Association named '#{ associations }' was not found on #{parent.active_record.name}; perhaps you misspelled it?"
+          raise ConfigurationError, "Association named '#{ associations }' was not found; perhaps you misspelled it?"
           unless join_association = find_join_association(reflection, parent)
             @reflections << reflection
             join_association = build_join_association(reflection, parent)
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index ea4856408da..0d7d28e4585 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -55,12 +55,7 @@ module ActiveRecord
 
         def find_parent_in(other_join_dependency)
           other_join_dependency.join_parts.detect do |join_part|
-            case parent
-            when JoinBase
-              parent.active_record == join_part.active_record
-            else
-              parent == join_part
-            end
+            parent == join_part
           end
         end
 
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index c2f0a82fd3a..3f880ce5e93 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -29,7 +29,7 @@ module ActiveRecord
     end
 
     class Merger
-      attr_reader :relation, :other
+      attr_reader :relation, :values
 
       def initialize(relation, other)
         if other.default_scoped? && other.klass != relation.klass
@@ -37,17 +37,13 @@ module ActiveRecord
         end
 
         @relation = relation
-        @other    = other
-      end
-
-      def values
-        @other.values
+        @values   = other.values
       end
 
       def normal_values
         Relation::SINGLE_VALUE_METHODS +
           Relation::MULTI_VALUE_METHODS -
-          [:where, :joins, :order, :bind, :reverse_order, :lock, :create_with, :reordering]
+          [:where, :order, :bind, :reverse_order, :lock, :create_with, :reordering]
       end
 
       def merge
@@ -58,7 +54,6 @@ module ActiveRecord
 
         merge_multi_values
         merge_single_values
-        merge_joins
 
         relation
       end
@@ -89,26 +84,6 @@ module ActiveRecord
         end
       end
 
-      def merge_joins
-        return if values[:joins].blank?
-
-        if other.klass == relation.klass
-          relation.joins!(values[:joins])
-        else
-          joins_to_stash, other_joins = values[:joins].partition { |join|
-            case join
-            when Hash, Symbol, Array
-              true
-            else
-              false
-            end
-          }
-
-          join_dependency = ActiveRecord::Associations::JoinDependency.new(other.klass, joins_to_stash, [])
-          relation.joins!(join_dependency.join_associations + other_joins)
-        end
-      end
-
       def merged_binds
         if values[:bind]
           (relation.bind_values + values[:bind]).uniq(&:first)
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 48fc82bbc7f..3ef357e2974 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -6,7 +6,6 @@ require 'models/topic'
 require 'models/comment'
 require 'models/author'
 require 'models/comment'
-require 'models/rating'
 require 'models/entrant'
 require 'models/developer'
 require 'models/reply'
@@ -20,7 +19,7 @@ require 'models/minivan'
 
 class RelationTest < ActiveRecord::TestCase
   fixtures :authors, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :posts, :comments,
-    :ratings, :tags, :taggings, :cars, :minivans
+    :tags, :taggings, :cars, :minivans
 
   def test_do_not_double_quote_string_id
     van = Minivan.last
@@ -732,12 +731,6 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal 1, comments.count
   end
 
-  def test_relation_merging_with_merged_joins
-    special_comments_with_ratings = SpecialComment.joins(:ratings)
-    posts_with_special_comments_with_ratings = Post.group("posts.id").joins(:special_comments).merge(special_comments_with_ratings)
-    assert_equal 1, authors(:david).posts.merge(posts_with_special_comments_with_ratings).to_a.length
-  end
-
   def test_count
     posts = Post.scoped