diff --git a/plugins/kolab_files/lib/kolab_files_engine.php b/plugins/kolab_files/lib/kolab_files_engine.php
index b8adfcbf..419dcb0b 100644
--- a/plugins/kolab_files/lib/kolab_files_engine.php
+++ b/plugins/kolab_files/lib/kolab_files_engine.php
@@ -939,7 +939,7 @@ class kolab_files_engine
                 $id = $attachment['id'];
 
                 // store new attachment in session
-                unset($attachment['status'], $attachment['abort']);
+                unset($attachment['data'], $attachment['status'], $attachment['abort']);
                 $COMPOSE['attachments'][$id] = $attachment;
 
                 if (($icon = $COMPOSE['deleteicon']) && is_file($icon)) {