diff --git a/scripts/upgrade b/scripts/upgrade
index 2490c80..b383b6b 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -39,8 +39,8 @@ if [ -z "${smtp_host:-}" ]; then
 		smtp_security=$(ynh_read_var_in_file --file=$user_conf --key=SMTP_SECURITY)
 		mail_return_path=$(ynh_read_var_in_file --file=$user_conf --key=MAIL_RETURN_PATH)
 		mail_sender=$(ynh_read_var_in_file --file=$user_conf --key=SMTP_SENDER)
-		sed -i "s@const SMTP_@//const SMTP_/@g" $user_conf
-		sed -i "s@const MAIL_@//const MAIL_/@g" $user_conf
+		ynh_replace_string --match_string="const SMTP_" --replace_string="//const SMTP_" --target_file=$user_conf
+		ynh_replace_string --match_string="const MAIL_" --replace_string="//const MAIL_" --target_file=$user_conf
 	else
 		smtp_host=$domain
 		smtp_port=25