diff --git a/tests/basic/models.py b/tests/basic/models.py
index 5496e6b409..86d0f0c4e4 100644
--- a/tests/basic/models.py
+++ b/tests/basic/models.py
@@ -32,4 +32,6 @@ class SelfRef(models.Model):
                                 related_name='+')
 
     def __str__(self):
+        # This method intentionally doesn't work for all cases - part
+        # of the test for ticket #20278
         return SelfRef.objects.get(selfref=self).pk