diff --git a/roles/ynh_backup/tasks/backup.yml b/roles/ynh_backup/tasks/backup.yml
index 9dbc153c863bab0fb25c523b89f814fe926383e3..91d27823bf79d487f6946c7a3608c074343545b0 100644
--- a/roles/ynh_backup/tasks/backup.yml
+++ b/roles/ynh_backup/tasks/backup.yml
@@ -20,7 +20,7 @@
 - name: Fail if variables are not used correctly
   ansible.builtin.fail:
     msg: You need to define variable ynh_backup.apps and / or ynh_backup.system to True
-  when: ynh_backup.apps is false and ynh_backup.system is false
+  when: ynh_backup.apps | default(False) is false and ynh_backup.system | default(False) is false
   tags: backup
 
 - name: Create backup folder if doesn't already exist