diff --git a/framework/Core/lib/Horde/Core/ActiveSync/Driver.php b/framework/Core/lib/Horde/Core/ActiveSync/Driver.php
index 2a033e0f40c..bf72b8dc17d 100644
--- a/framework/Core/lib/Horde/Core/ActiveSync/Driver.php
+++ b/framework/Core/lib/Horde/Core/ActiveSync/Driver.php
@@ -1774,6 +1774,9 @@ public function changeMessage($folderid, $id, Horde_ActiveSync_Message_Base $mes
                     $stat['flags'] = array_merge($stat['flags'], array('flagged' => $message->flag->flagstatus));
                 }
                 if ($message->propertyExists('categories')) {
+                    // We *try* to make sure the category is added as a custom
+                    // IMAP flag. This might fail in some edge cases, like e.g.
+                    // with non-ascii characters.
                     $this->_connector->mail_ensureMessageFlags($message->categories);
                     $this->_imap->categoriesToFlags($folderid, $message->categories, $id);
                     $stat['categories'] = $message->categories;