diff --git a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
index fb59f63f911a7845367a43d47bba167c37eb6bec..d75791cab98c18182c07fd4b3955259693780a4f 100644
--- a/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
+++ b/activerecord/test/cases/associations/eager_load_includes_full_sti_class_test.rb
@@ -27,6 +27,7 @@ def test_class_names
     post = Namespaced::Post.find_by_title( 'Great stuff', :include => :tagging )
     assert_nil post.tagging
 
+    ActiveRecord::IdentityMap.clear
     ActiveRecord::Base.store_full_sti_class = true
     post = Namespaced::Post.find_by_title( 'Great stuff', :include => :tagging )
     assert_instance_of Tagging, post.tagging