diff --git a/colab/accounts/utils/mailman.py b/colab/accounts/utils/mailman.py
index 949813d..bf69207 100644
--- a/colab/accounts/utils/mailman.py
+++ b/colab/accounts/utils/mailman.py
@@ -76,6 +76,8 @@ def mailing_lists(**kwargs):
 
     try:
         lists = requests.get(url, timeout=TIMEOUT, params=kwargs)
+        if not isinstance(lists, (list, tuple)):
+            raise
     except:
         LOGGER.exception('Unable to list mailing lists')
         return []
--
libgit2 0.21.2