diff --git a/django/contrib/auth/tests/forms.py b/django/contrib/auth/tests/forms.py
index 9b557d18bf..429967cba0 100644
--- a/django/contrib/auth/tests/forms.py
+++ b/django/contrib/auth/tests/forms.py
@@ -260,7 +260,10 @@ class PasswordResetFormTest(TestCase):
             data = {'email': 'testclient@example.com'}
             form = PasswordResetForm(data)
             self.assertTrue(form.is_valid())
-            form.save()
+            # Since we're not providing a request object, we must provide a
+            # domain_override to prevent the save operation from failing in the
+            # potential case where contrib.sites is not installed. Refs #16412.
+            form.save(domain_override='example.com')
             self.assertEqual(len(mail.outbox), 1)
             self.assertEqual(mail.outbox[0].subject, u'Custom password reset on example.com')