diff --git a/scripts/upgrade b/scripts/upgrade
index 4f9f42c..af55559 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -29,7 +29,7 @@ ynh_systemd_action --service_name=$app --action="stop" --log_path="systemd"
 #=================================================
 ynh_script_progression --message="Ensuring downward compatibility..." --weight=1
 
-if [ -z "$enable_registrations" ]; then
+if [ -z "${enable_registrations:-}" ]; then
 	enable_registrations="false"
 	ynh_app_setting_set --app=$app --key=enable_registrations --value=$enable_registrations
 fi