diff --git a/kronolith/lib/Event.php b/kronolith/lib/Event.php
index 9a102d76105..206d4641705 100644
--- a/kronolith/lib/Event.php
+++ b/kronolith/lib/Event.php
@@ -795,8 +795,7 @@ public function toiCalendar($calendar)
 
             // Tags
             if ($this->tags) {
-                $tags = implode(', ', $this->tags);
-                $vEvent->setAttribute('CATEGORIES', $tags);
+                $vEvent->setAttribute('CATEGORIES', '', array(), true, $this->tags);
             }
 
             // Location
diff --git a/mnemo/lib/Driver.php b/mnemo/lib/Driver.php
index 96628e73071..4d8e50840d9 100644
--- a/mnemo/lib/Driver.php
+++ b/mnemo/lib/Driver.php
@@ -468,7 +468,7 @@ public function toiCalendar($memo, $calendar)
         $vnote->setAttribute('SUMMARY', $memo['desc']);
 
         if (!empty($memo['tags'])) {
-            $vnote->setAttribute('CATEGORIES', implode(', ', $memo['tags']));
+            $vnote->setAttribute('CATEGORIES', '', array(), true, $memo['tags']);
         }
 
         /* Get the note's history. */
diff --git a/nag/lib/Task.php b/nag/lib/Task.php
index 8ed63d1e17a..3a250c94c76 100644
--- a/nag/lib/Task.php
+++ b/nag/lib/Task.php
@@ -1278,7 +1278,7 @@ public function toiCalendar(Horde_Icalendar $calendar)
         }
 
         if ($this->tags) {
-            $vTodo->setAttribute('CATEGORIES', implode(', ', $this->tags));
+            $vTodo->setAttribute('CATEGORIES', '', array(), true, $this->tags);
         }
 
         /* Get the task's history. */