diff --git a/src/allmydata/test/test_client.py b/src/allmydata/test/test_client.py
index 36d73692d..82516c8de 100644
--- a/src/allmydata/test/test_client.py
+++ b/src/allmydata/test/test_client.py
@@ -648,7 +648,8 @@ class IntroducerClients(unittest.TestCase):
 
     def test_invalid_introducer_furl(self):
         """
-        An introducer.furl of 'None' is invalid
+        An introducer.furl of 'None' is invalid and causes
+        create_introducer_clients to fail.
         """
         cfg = (
             "[client]\n"