diff --git a/activerecord/lib/active_record/associations/through_association_scope.rb b/activerecord/lib/active_record/associations/through_association_scope.rb
index 5dc5b0c048e036eaf8a3e36ba63b0c2aaf305929..99920d4c630c169d60f47ad09e92857a87d2b67f 100644
--- a/activerecord/lib/active_record/associations/through_association_scope.rb
+++ b/activerecord/lib/active_record/associations/through_association_scope.rb
@@ -106,7 +106,12 @@ def construct_join_attributes(associate)
         # TODO: revisit this to allow it for deletion, supposing dependent option is supported
         raise ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(@owner, @reflection) if [:has_one, :has_many].include?(@reflection.source_reflection.macro)
 
-        join_attributes = construct_owner_attributes(@reflection.through_reflection).merge(@reflection.source_reflection.primary_key_name => associate.id)
+        join_attributes = construct_owner_attributes(@reflection.through_reflection)
+
+        join_attributes.merge!(
+          @reflection.source_reflection.primary_key_name =>
+            associate.send(@reflection.source_reflection.association_primary_key)
+        )
 
         if @reflection.options[:source_type]
           join_attributes.merge!(@reflection.source_reflection.options[:foreign_type] => associate.class.base_class.name)
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 816b43ab9ee55898c5d62681230756079df2dcc5..d2372734649625aa5e57abefe3e18f0831dc1773 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -21,7 +21,7 @@
 require 'models/category'
 
 class HasManyThroughAssociationsTest < ActiveRecord::TestCase
-  fixtures :posts, :readers, :people, :comments, :authors,
+  fixtures :posts, :readers, :people, :comments, :authors, :categories,
            :owners, :pets, :toys, :jobs, :references, :companies,
            :subscribers, :books, :subscriptions, :developers, :categorizations
 
@@ -397,6 +397,34 @@ def test_has_many_association_through_a_has_many_association_to_self
     assert_equal people(:susan).agents.map(&:agents).flatten, people(:susan).agents_of_agents
   end
 
+  def test_associate_existing_with_nonstandard_primary_key_on_belongs_to
+    Categorization.create(:author => authors(:mary), :named_category_name => categories(:general).name)
+    assert_equal categories(:general), authors(:mary).named_categories.first
+  end
+
+  def test_collection_build_with_nonstandard_primary_key_on_belongs_to
+    author   = authors(:mary)
+    category = author.named_categories.build(:name => "Primary")
+    author.save
+    assert Categorization.exists?(:author_id => author.id, :named_category_name => category.name)
+    assert author.named_categories(true).include?(category)
+  end
+
+  def test_collection_create_with_nonstandard_primary_key_on_belongs_to
+    author   = authors(:mary)
+    category = author.named_categories.create(:name => "Primary")
+    assert Categorization.exists?(:author_id => author.id, :named_category_name => category.name)
+    assert author.named_categories(true).include?(category)
+  end
+
+  def test_collection_delete_with_nonstandard_primary_key_on_belongs_to
+    author   = authors(:mary)
+    category = author.named_categories.create(:name => "Primary")
+    author.named_categories.delete(category)
+    assert !Categorization.exists?(:author_id => author.id, :named_category_name => category.name)
+    assert author.named_categories(true).empty?
+  end
+
   def test_collection_singular_ids_getter_with_string_primary_keys
     book = books(:awdr)
     assert_equal 2, book.subscriber_ids.size
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 244c5ac4f58bd76b5b22822091723f03d0feee34..83a6f5d926898deaedf03e5e66a8397910b62ad3 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -78,6 +78,7 @@ def testing_proxy_target
 
   has_many :categorizations
   has_many :categories, :through => :categorizations
+  has_many :named_categories, :through => :categorizations
 
   has_many :special_categorizations
   has_many :special_categories, :through => :special_categorizations, :source => :category
diff --git a/activerecord/test/models/categorization.rb b/activerecord/test/models/categorization.rb
index fdb0a1154097f32701001af6c951357eeadd6d3f..45f50e4af32454febd2b24ad0a07039896caf27c 100644
--- a/activerecord/test/models/categorization.rb
+++ b/activerecord/test/models/categorization.rb
@@ -1,6 +1,7 @@
 class Categorization < ActiveRecord::Base
   belongs_to :post
   belongs_to :category
+  belongs_to :named_category, :class_name => 'Category', :foreign_key => :named_category_name, :primary_key => :name
   belongs_to :author
 
   belongs_to :author_using_custom_pk,  :class_name => 'Author', :foreign_key => :author_id, :primary_key => :author_address_extra_id
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 99761a4160fcd154ac4a5c31d3e67c5ceda6868a..3dea7e149252052481efb8420d3dff7e1dca9859 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -110,6 +110,7 @@ def create_table(*args, &block)
 
   create_table :categorizations, :force => true do |t|
     t.column :category_id, :integer
+    t.string :named_category_name
     t.column :post_id, :integer
     t.column :author_id, :integer
     t.column :special, :boolean