3 files changed, 19 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/association_preload.rb b/activerecord/lib/active_record/association_preload.rb
index 9d0bf3a308..195d2fb4f8 100644
--- a/activerecord/lib/active_record/association_preload.rb
+++ b/activerecord/lib/active_record/association_preload.rb
@@ -229,7 +229,7 @@ module ActiveRecord
         options = reflection.options
 
         primary_key_name = reflection.through_reflection_primary_key_name
-        id_to_record_map, ids = construct_id_map(records, primary_key_name)
+        id_to_record_map, ids = construct_id_map(records, primary_key_name || reflection.options[:primary_key])
         records.each {|record| record.send(reflection.name).loaded}
 
         if options[:through]
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 5a60b13fd8..237e5c0e9d 100755
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -2171,7 +2171,7 @@ module ActiveRecord
                         aliased_table_name,
                         foreign_key,
                         parent.aliased_table_name,
-                        parent.primary_key
+                        reflection.options[:primary_key] || parent.primary_key
                       ]
                   end
                 when :belongs_to
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index afbd9fddf9..ff3d6ece05 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -786,4 +786,21 @@ class EagerAssociationTest < ActiveRecord::TestCase
       assert_equal Person.find(person.id).agents, person.agents
     end
   end
+
+  def test_preload_has_many_using_primary_key
+    expected = Firm.find(:first).clients_using_primary_key.to_a
+    firm = Firm.find :first, :include => :clients_using_primary_key
+    assert_no_queries do
+      assert_equal expected, firm.clients_using_primary_key
+    end
+  end
+
+  def test_include_has_many_using_primary_key
+    expected = Firm.find(1).clients_using_primary_key.sort_by &:name
+    firm = Firm.find 1, :include => :clients_using_primary_key, :order => 'clients_using_primary_keys_companies.name'
+    assert_no_queries do
+      assert_equal expected, firm.clients_using_primary_key
+    end
+  end
+  
 end