diff --git a/tests/regressiontests/generic_views/edit.py b/tests/regressiontests/generic_views/edit.py
index 182615a86b..2bd982e3d9 100644
--- a/tests/regressiontests/generic_views/edit.py
+++ b/tests/regressiontests/generic_views/edit.py
@@ -126,6 +126,10 @@ class UpdateViewTests(TestCase):
 
         res = self.client.put('/edit/author/%d/update/' % a.pk,
                         {'name': 'Randall Munroe (author of xkcd)', 'slug': 'randall-munroe'})
+        # Here is the expected failure. PUT data are not processed in any special
+        # way by django. So the request will equal to a POST without data, hence
+        # the form will be invalid and redisplayed with errors (status code 200).
+        # See also #12635
         self.assertEqual(res.status_code, 302)
         self.assertRedirects(res, 'http://testserver/list/authors/')
         self.assertQuerysetEqual(Author.objects.all(), ['<Author: Randall Munroe (author of xkcd)>'])