diff --git a/scripts/upgrade b/scripts/upgrade
index cc28cec..2e07065 100644
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -32,6 +32,10 @@ upstream_version=$(ynh_app_upstream_version)
 
 domain=$(ynh_app_setting_get $app special_domain)
 server_name=$(ynh_app_setting_get $app server_name)
+if [ -z $server_name ]; then     # for retro compatibility
+   server_name=$domain
+   ynh_app_setting_set $app server_name  $domain
+fi
 path_url=$(ynh_app_setting_get $app special_path)
 final_path=$(ynh_app_setting_get $app final_path)
 synapse_old_version=$(ynh_app_setting_get $app synapse_version)