diff --git a/core/admin/mailu/configuration.py b/core/admin/mailu/configuration.py
index 2136e624..c1444ee5 100644
--- a/core/admin/mailu/configuration.py
+++ b/core/admin/mailu/configuration.py
@@ -2,6 +2,7 @@ import os
 
 from datetime import timedelta
 from socrate import system
+import ipaddress
 
 DEFAULT_CONFIG = {
     # Specific to the admin UI