--- a/src/pyams_security/zmi/notification.py	Tue Nov 15 10:34:41 2016 +0100
+++ b/src/pyams_security/zmi/notification.py	Tue Nov 15 10:35:49 2016 +0100
@@ -72,7 +72,8 @@
 
     def updateWidgets(self, prefix=None):
         super(SecurityManagerNotificationsEditForm, self).updateWidgets(prefix)
-        self.widgets['signature'].label_css_class = 'textarea'
+        if 'signature' in self.widgets:
+            self.widgets['signature'].widget_css_class = 'textarea'
 
 
 @view_config(name='notifications.json', context=ISecurityManager, request_type=IPyAMSLayer,