diff --git a/contrib/os-services/roles/prepare/tasks/main.yml b/contrib/os-services/roles/prepare/tasks/main.yml
index ddae80ce9eb..cf7262234a7 100644
--- a/contrib/os-services/roles/prepare/tasks/main.yml
+++ b/contrib/os-services/roles/prepare/tasks/main.yml
@@ -20,4 +20,4 @@
       "'ufw.service' in services"
 
   when:
-  - disable_service_firewall
+  - disable_service_firewall is defined and disable_service_firewall