diff --git a/filemanager/inc/class.filemanager_hooks.inc.php b/filemanager/inc/class.filemanager_hooks.inc.php
index 2dfe969648..e531a517d2 100644
--- a/filemanager/inc/class.filemanager_hooks.inc.php
+++ b/filemanager/inc/class.filemanager_hooks.inc.php
@@ -236,7 +236,7 @@ class filemanager_hooks
 				'help'   => lang('Excludes selected mime types from being opened by editor'),
 				'name'   => 'collab_excluded_mimes',
 				'values' => $mimes,
-				'default' => '',
+				'default' => 'application/pdf',
 				'attributes' => array(
 					'autocompelete_url' => ' ',
 					'autocomplete_params' => ' ',