diff --git a/scripts/upgrade b/scripts/upgrade
index b1233c8b..66ad8d17 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -15,8 +15,6 @@ source /usr/share/yunohost/helpers
 ynh_script_progression --message="Loading settings..." --weight=1
 
 email=$(ynh_user_get_info --username=$admin --key=mail)
-random_string=$(ynh_app_setting_get --app=$app --key=random_string)
-
 
 #=================================================
 # CHECK VERSION
@@ -32,7 +30,7 @@ upgrade_type=$(ynh_check_app_version_changed)
 ynh_script_progression --message="Ensuring downward compatibility..." --weight=1
 
 # If random_string doesn't exist, create it
-if [ -z "$random_string" ]; then
+if [ -z "${random_string:-}" ]; then
     random_string="$(ynh_string_random --length=48)"
     ynh_app_setting_set --app=$app --key=random_string --value=$random_string
 fi