diff --git a/ad2web/notifications/types.py b/ad2web/notifications/types.py
index 49c2bda..bdbf118 100644
--- a/ad2web/notifications/types.py
+++ b/ad2web/notifications/types.py
@@ -452,7 +452,7 @@ def _build_panel_state(self):
 
         # HACK: do not allow parsing of last_message_received as XML it is cdata
         cdel = Element("last_message_received")
-        cdel.append(Comment(' --><![CDATA[' + current_app.decoder.last_message_received or "" + ']]><!-- '))
+        cdel.append(Comment(' --><![CDATA[' + (current_app.decoder.last_message_received or "") + ']]><!-- '))
         el.append(cdel)
 
         return tostring(el)