diff --git a/lib/activityhandlerplugin.php b/lib/activityhandlerplugin.php
index 9ebcd8a218..e1779bbe6a 100644
--- a/lib/activityhandlerplugin.php
+++ b/lib/activityhandlerplugin.php
@@ -557,7 +557,7 @@ abstract class ActivityHandlerPlugin extends Plugin
             $class .= ' limited-scope';
         }
         try {
-            $class .= ' notice-source-'.common_to_alphanumeric($this->notice->source);
+            $class .= ' notice-source-'.common_to_alphanumeric($nli->notice->source);
         } catch (Exception $e) {
             // either source or what we filtered out was a zero-length string
         }