diff --git a/application/config/config.php b/application/config/config.php
index 0608348..3114f41 100644
--- a/application/config/config.php
+++ b/application/config/config.php
@@ -282,7 +282,7 @@
 | 'sess_driver'				= the driver to load: cookie (Classic), native (PHP sessions),
 |	or your custom driver name
 | 'sess_valid_drivers'		= additional valid drivers which may be loaded
-| 'sess_cookie_name'		= the name you want for the cookie
+| 'sess_cookie_name'		= the name you want for the cookie, must contain only [0-9a-z_-] characters
 | 'sess_expiration'			= the number of SECONDS you want the session to last.
 |   by default sessions last 7200 seconds (two hours).  Set to zero for no expiration.
 | 'sess_expire_on_close'	= Whether to cause the session to expire automatically
@@ -435,4 +435,4 @@
 
 
 /* End of file config.php */
-/* Location: ./application/config/config.php */
\ No newline at end of file
+/* Location: ./application/config/config.php */