diff --git a/application/config/config.php b/application/config/config.php
index a4d883f..479d591 100644
--- a/application/config/config.php
+++ b/application/config/config.php
@@ -344,6 +344,9 @@
 |
 |	Whether to match the user's IP address when reading the session data.
 |
+|	WARNING: If you're using the database driver, don't forget to update
+|	         your session table's PRIMARY KEY when changing this setting.
+|
 | 'sess_time_to_update'
 |
 |	How many seconds between CI regenerating the session ID.