diff --git a/product/ERP5Form/ListBox.py b/product/ERP5Form/ListBox.py
index d8c1014634390fa19866b1a7a0e1240cdb5407cb..4afd6a84e548cca48ed70c2174891d413517229d 100755
--- a/product/ERP5Form/ListBox.py
+++ b/product/ERP5Form/ListBox.py
@@ -882,11 +882,13 @@ class ListBoxWidget(Widget.Widget):
               base_category = domain.split('/')[0]
               if portal_categories is not None:
                 if base_category in portal_categories.objectIds():
-                  root = root_dict[base_category] = portal_categories.restrictedTraverse(domain)
+                  root = portal_categories.restrictedTraverse(domain, None)
+                  if root is not None :
+                    root_dict[base_category] = root
               if root is None and portal_domains is not None:
                 if base_category in portal_domains.objectIds():
                   base_domain = portal_domains.getDomainByPath(domain)
-                  root =  base_domain
+                  root = base_domain
                   root_dict[base_category] = base_domain.getRelativeUrl()
               if root is None:
                 try: