diff --git a/addons/auth_ldap/users_ldap.py b/addons/auth_ldap/users_ldap.py
index 6a6414c0037..4ab6a918382 100644
--- a/addons/auth_ldap/users_ldap.py
+++ b/addons/auth_ldap/users_ldap.py
@@ -96,7 +96,11 @@ class CompanyLDAP(osv.osv):
             return False
 
         entry = False
-        filter = filter_format(conf['ldap_filter'], (login,))
+        try:
+            filter = filter_format(conf['ldap_filter'], (login,))
+        except TypeError:
+            _logger.warning('Could not format LDAP filter. Your filter should contain one \'%s\'.')
+            return False
         try:
             results = self.query(conf, filter)