diff --git a/wcs/admin/forms.py b/wcs/admin/forms.py
index 8402cd328..77a8bfa65 100644
--- a/wcs/admin/forms.py
+++ b/wcs/admin/forms.py
@@ -1158,7 +1158,7 @@ class FormDefPage(Directory):
             form.add(CheckboxWidget, 'force', title=_('Overwrite despite data loss'))
         else:
             form.add_hidden('force', 'ok')
-        form.add_hidden('new_formdef', ET.tostring(new_formdef.export_to_xml(include_id=True)))
+        form.add_hidden('new_formdef', force_str(ET.tostring(new_formdef.export_to_xml(include_id=True))))
         form.add_submit('submit', _('Submit'))
         form.add_submit('cancel', _('Cancel'))
         r += form.render()