--- a/src/pyams_content/shared/form/zmi/properties.py	Wed Apr 11 16:44:46 2018 +0200
+++ b/src/pyams_content/shared/form/zmi/properties.py	Wed Apr 11 16:46:31 2018 +0200
@@ -36,6 +36,8 @@
 class FormPropertiesEditForm(InnerAdminEditForm):
     """Form properties edit form extension"""
 
+    prefix = 'form_properties.'
+
     legend = _("Main form settings")
     fieldset_class = 'bordered no-x-margin margin-y-10'
 
@@ -49,8 +51,10 @@
 
     def get_ajax_output(self, changes):
         if 'handler' in changes.get(IWfForm, ()):
-            return {'status': 'reload',
-                    'message': self.request.localizer.translate(self.successMessage)}
+            return {
+                'status': 'reload',
+                'message': self.request.localizer.translate(self.successMessage)
+            }
         else:
             return super(FormPropertiesEditForm, self).get_ajax_output(changes)
 
@@ -61,6 +65,8 @@
 class FormHandlerPropertiesEditForm(InnerAdminEditForm):
     """Form handler properties edit form extension"""
 
+    prefix = 'form_handler.'
+
     legend = _("Form handler settings")
     fieldset_class = 'bordered no-x-margin margin-y-10'