diff --git a/plugins/Autocomplete/readme.txt b/plugins/Autocomplete/readme.txt
index 3272aa1eef..1db4c65658 100644
--- a/plugins/Autocomplete/readme.txt
+++ b/plugins/Autocomplete/readme.txt
@@ -1,5 +1,7 @@
 Autocomplete allows users to autocomplete screen names in @ replies. When an "@" is typed into the notice text area, an autocomplete box is displayed populated with the user's friends' screen names.
 
+Note: This plugin doesn't work if the site is in Private mode, i.e. when $config['site']['private'] is set to true.
+
 Installation
 ============
 Add "addPlugin('Autocomplete');" to the bottom of your config.php