diff --git a/htdocs/install/mysql/migration/10.0.0-11.0.0.sql b/htdocs/install/mysql/migration/10.0.0-11.0.0.sql
index 4ec9fbdaffb..f8cc3062bde 100644
--- a/htdocs/install/mysql/migration/10.0.0-11.0.0.sql
+++ b/htdocs/install/mysql/migration/10.0.0-11.0.0.sql
@@ -49,4 +49,4 @@ ALTER TABLE llx_facture_fourn DROP COLUMN total;
 ALTER TABLE llx_user ADD COLUMN iplastlogin         varchar(250);
 ALTER TABLE llx_user ADD COLUMN ippreviouslogin     varchar(250);
 
-ALTER TABLE llx_events ADD COLUMN prefix_session varchar(250) NULL;
+ALTER TABLE llx_events ADD COLUMN prefix_session varchar(255) NULL;