diff --git a/upgrade.txt b/upgrade.txt
index f525a2a..78047e9 100644
--- a/upgrade.txt
+++ b/upgrade.txt
@@ -4,7 +4,7 @@
 - Backup you database
 - Make a copy from your SemanticScuttle Web directory
 - Upgrade your database by following instructions ONE after ONE (order is important) :
-* ALTER TABLE `sc_bookmarks` ADD `bPrivateNote` VARCHAR( 1500 ) NOT NULL AFTER `bDescription` ;
+* ALTER TABLE `sc_bookmarks` ADD `bPrivateNote` VARCHAR( 1500 ) NULL AFTER `bDescription` ;
 
 - Upgrade your current configuration file (config.inc.php) with respect to config.inc.php.example
 * Add variable : $descriptionAnchors = array("author", "isbn", "address"=>"[address][street][/street][city][/city][/address]"); #add a possible anchor (structured content) for bookmarks' description field