diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index ec7af7913dc81701d1273cd29673933990f2ec8b..552c1ed06e84528bcfb1202926a56d4f712b011f 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -163,11 +163,6 @@ def find_target
         end
 
       private
-        # Array#flatten has problems with recursive arrays. Going one level deeper solves the majority of the problems.
-        def flatten_deeper(array)
-          array.collect { |element| element.respond_to?(:flatten) ? element.flatten : element }.flatten
-        end
-        
         def callback(method, record)
           callbacks_for(method).each do |callback|
             case callback
diff --git a/activerecord/lib/active_record/associations/association_proxy.rb b/activerecord/lib/active_record/associations/association_proxy.rb
index c093e40ca0f5b605b1ff49379425147382c647c0..1d313fc537fc140a8e2d7753bdfd19d125c4c8db 100644
--- a/activerecord/lib/active_record/associations/association_proxy.rb
+++ b/activerecord/lib/active_record/associations/association_proxy.rb
@@ -146,6 +146,11 @@ def raise_on_type_mismatch(record)
             raise ActiveRecord::AssociationTypeMismatch, "#{@reflection.class_name} expected, got #{record.class}"
           end
         end
+
+        # Array#flatten has problems with recursive arrays. Going one level deeper solves the majority of the problems.
+        def flatten_deeper(array)
+          array.collect { |element| element.respond_to?(:flatten) ? element.flatten : element }.flatten
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index b5feeff1d29b0c590d2090c68826ac34553934c0..0257b1857dc9d15e46dee6388b28cfb4abeb91ba 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -44,18 +44,26 @@ def reset
       # must have ids in order to create records associating them, so this
       # will raise ActiveRecord::HasManyThroughCantAssociateNewRecords if
       # either is a new record.  Calls create! so you can rescue errors.
-      def <<(*args)
-        return if args.empty?
+      #
+      # The :before_add and :after_add callbacks are not yet supported.
+      def <<(*records)
+        return if records.empty?
         through = @reflection.through_reflection
         raise ActiveRecord::HasManyThroughCantAssociateNewRecords.new(@owner, through) if @owner.new_record?
 
+        load_target
+
         klass = through.klass
         klass.transaction do
-          args.each do |associate|
+          flatten_deeper(records).each do |associate|
+            raise_on_type_mismatch(associate)
             raise ActiveRecord::HasManyThroughCantAssociateNewRecords.new(@owner, through) unless associate.respond_to?(:new_record?) && !associate.new_record?
-            klass.with_scope(:create => construct_join_attributes(associate)) { klass.create! }
+
+            @target << klass.with_scope(:create => construct_join_attributes(associate)) { klass.create! }
           end
         end
+
+        self
       end
 
       [:push, :concat].each { |method| alias_method method, :<< }
diff --git a/activerecord/test/associations_join_model_test.rb b/activerecord/test/associations_join_model_test.rb
index 0f6a5e76c297a34955408ede17933ec6cc901691..1a0882fcfb3afe958b1a37b0327fdeada0d6a243 100644
--- a/activerecord/test/associations_join_model_test.rb
+++ b/activerecord/test/associations_join_model_test.rb
@@ -373,15 +373,28 @@ def test_create_associate_when_adding_to_has_many_through
     count = posts(:thinking).tags.count
     push = Tag.create!(:name => 'pushme')
     assert_nothing_raised { posts(:thinking).tags << push }
+    assert_equal(count + 1, posts(:thinking).tags.size)
     assert_equal(count + 1, posts(:thinking).tags(true).size)
 
     assert_nothing_raised { posts(:thinking).tags.create!(:name => 'foo') }
+    assert_equal(count + 2, posts(:thinking).tags.size)
     assert_equal(count + 2, posts(:thinking).tags(true).size)
 
     assert_nothing_raised { posts(:thinking).tags.concat(Tag.create!(:name => 'abc'), Tag.create!(:name => 'def')) }
+    assert_equal(count + 4, posts(:thinking).tags.size)
     assert_equal(count + 4, posts(:thinking).tags(true).size)
   end
 
+  def test_adding_junk_to_has_many_through_should_raise_type_mismatch
+    assert_raise(ActiveRecord::AssociationTypeMismatch) { posts(:thinking).tags << "Uhh what now?" }
+  end
+
+  def test_adding_to_has_many_through_should_return_self
+    tags = posts(:thinking).tags
+    assert_equal tags, posts(:thinking).tags.push(tags(:general))
+  end
+
+
   def test_has_many_through_sum_uses_calculations
     assert_nothing_raised { authors(:david).comments.sum(:post_id) }
   end