diff --git a/activerecord/test/cases/associations/has_one_through_associations_test.rb b/activerecord/test/cases/associations/has_one_through_associations_test.rb
index 90c557e886d3889523913ad69726f4923c1c083e..01a4137a5df39cabf05c269ea6414dc5e0e57cc0 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -191,6 +191,7 @@ def test_reassigning_has_one_through
   end
 
   def test_preloading_has_one_through_on_belongs_to
+    MemberDetail.delete_all
     assert_not_nil @member.member_type
     @organization = organizations(:nsa)
     @member_detail = MemberDetail.new