diff --git a/config/global.php b/config/global.php
index 23c51bc4c5243f2d120678f1a36915423f648eae..a54565498fcd5ffa016e08475ef5727207b2769d 100644
--- a/config/global.php
+++ b/config/global.php
@@ -73,6 +73,7 @@ return array(
             ))));
     },
 
+    // contains RequestProcessor instances, currently used by Piwik\Tracker\Visit
     'tracker.request.processors' => array(),
 
     'Piwik\Tracker\VisitorRecognizer' => DI\object()