diff --git a/product/ERP5Type/RoleProviderBase.py b/product/ERP5Type/RoleProviderBase.py
index f63207f094f08a61a37d42ebb39052880dbe3be7..92ddd1be7c4046f7cf1f26220fdbbef563cc1633 100644
--- a/product/ERP5Type/RoleProviderBase.py
+++ b/product/ERP5Type/RoleProviderBase.py
@@ -90,6 +90,7 @@ class RoleProviderBase:
                  , condition
                  , category
                  , base_category_script
+                 # XXX Default value is a tuple, but a string is required
                  , base_category=()
                  , REQUEST=None
                  ):