diff --git a/admin_manual/configuration/custom_mount_config_gui.rst b/admin_manual/configuration/custom_mount_config_gui.rst
index 437bc6770..9373df8ec 100644
--- a/admin_manual/configuration/custom_mount_config_gui.rst
+++ b/admin_manual/configuration/custom_mount_config_gui.rst
@@ -55,7 +55,8 @@ Local Storage
 -------------
 
 Use this to mount any directory on your ownCloud server that is outside of your 
-ownCloud ``data/`` directory. 
+ownCloud ``data/`` directory. This directory must be readable and writable by 
+your HTTP server user.
 
 In the ``Folder name`` field enter the folder name that you want to appear on 
 your ownCloud ``Files`` page.