diff --git a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
index 67e18d6..fba8fde 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -8,7 +8,7 @@ module ActiveRecord
           @target = (AssociationProxy === record ? record.target : record)
 
           @owner[@reflection.primary_key_name] = record_id(record)
-          @owner[@reflection.options[:foreign_type]] = record.class.base_class.name.to_s
+          @owner[@reflection.options[:foreign_type]] = record.class.name.to_s
 
           @updated = true
         end
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 9f3945f..0a6e5d5 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -14,6 +14,7 @@ require 'models/tagging'
 require 'models/comment'
 require 'models/sponsor'
 require 'models/member'
+require 'models/special_member'
 require 'models/essay'
 
 class BelongsToAssociationsTest < ActiveRecord::TestCase
@@ -358,7 +359,21 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     sponsor.sponsorable = member
     assert_equal "Member", sponsor.sponsorable_type
   end
+  
+  def test_polymorphic_assignment_foreign_type_field_updating_with_single_table_inheritence
+    # should update when assigning a saved record
+    sponsor = Sponsor.new
+    member = SpecialMember.create
+    sponsor.sponsorable = member
+    assert_equal "SpecialMember", sponsor.sponsorable_type
 
+    # should update when assigning a new record
+    sponsor = Sponsor.new
+    member = SpecialMember.new
+    sponsor.sponsorable = member
+    assert_equal "SpecialMember", sponsor.sponsorable_type
+  end
+  
   def test_polymorphic_assignment_with_primary_key_foreign_type_field_updating
     # should update when assigning a saved record
     essay = Essay.new