diff --git a/inventory/group_vars/all/all.yml b/inventory/group_vars/all/all.yml
index ce72829580..7546e2e67f 100644
--- a/inventory/group_vars/all/all.yml
+++ b/inventory/group_vars/all/all.yml
@@ -127,4 +127,7 @@ ansible_ssh_extra_args: >
   -T
 
 # Toggle whether the service is deployed in a container or not
-is_metal: "{{ properties.is_metal | default(false) }}"
+is_metal: >-
+  {{ (properties is defined) and
+     (properties.is_metal is defined) and
+     (properties.is_metal | bool) }}
diff --git a/inventory/group_vars/galera_all.yml b/inventory/group_vars/galera_all.yml
index 08a8da382b..9bb3fd1051 100644
--- a/inventory/group_vars/galera_all.yml
+++ b/inventory/group_vars/galera_all.yml
@@ -25,7 +25,7 @@ galera_container_bind_mounts:
 
 # Disable PrivateDevices for MariaDB on CentOS 7
 # See https://bugs.launchpad.net/openstack-ansible/+bug/1697531 for details.
-galera_disable_privatedevices: "{{ ((properties.is_metal | default(false)) | bool) | ternary('false', 'true') }}"
+galera_disable_privatedevices: "{{ not is_metal }}"
 
 # By default galera_monitoring xinetd app is open to 0.0.0.0/0
 # This makes sure the monitoring is only restricted to the necessary nodes:
diff --git a/inventory/group_vars/memcached.yml b/inventory/group_vars/memcached.yml
index f6e861f079..98f062684b 100644
--- a/inventory/group_vars/memcached.yml
+++ b/inventory/group_vars/memcached.yml
@@ -20,4 +20,4 @@ memcached_package_state: "{{ package_state }}"
 
 # Disable PrivateDevices for MemcacheD on CentOS 7
 # See https://bugs.launchpad.net/openstack-ansible/+bug/1697531 for details.
-memcached_disable_privatedevices: "{{ ((properties.is_metal | default(false)) | bool) | ternary('false', 'true') }}"
+memcached_disable_privatedevices: "{{ not is_metal }}"