diff --git a/roles/backup_server/tasks/main.yml b/roles/backup_server/tasks/main.yml
index 8f816272123687071d0caaa10a796b3fe9d14dbc..a77ff31150051e0956d88b102289b85ab4d88c42 100644
--- a/roles/backup_server/tasks/main.yml
+++ b/roles/backup_server/tasks/main.yml
@@ -13,7 +13,7 @@
     state: directory
     owner: root
     group: root
-    mode: 0751
+    mode: "0751"
 
 - name: Create backup client groups
   group:
@@ -40,7 +40,7 @@
     state: directory
     owner: root
     group: "{{ item.server | replace('.', '_') | regex_replace('^', 'bak-') }}"
-    mode: 0750
+    mode: "0750"
   with_items: "{{ backup_clients }}"
 
 - name: Create duplicity directories for backup client users
@@ -49,7 +49,7 @@
     state: directory
     owner: "{{ item.server | replace('.', '_') | regex_replace('^', 'bak-') }}"
     group: "{{ item.server | replace('.', '_') | regex_replace('^', 'bak-') }}"
-    mode: 0770
+    mode: "0770"
   with_items: "{{ backup_clients }}"
 
 - name: Create SSH directory for backup client users
@@ -58,7 +58,7 @@
     state: directory
     owner: root
     group: root
-    mode: 0751
+    mode: "0751"
   with_items: "{{ backup_clients }}"
 
 - name: Populate authorized keys for backup client users
@@ -75,7 +75,7 @@
     state: file
     owner: root
     group: "{{ item.server | replace('.', '_') | regex_replace('^', 'bak-') }}"
-    mode: 0640
+    mode: "0640"
   with_items: "{{ backup_clients }}"
 
 - name: Deny the backup group login via regular SSH
@@ -92,7 +92,7 @@
     state: directory
     owner: root
     group: root
-    mode: 0700
+    mode: "0700"
 
 - name: Deploy configuration file for the backup OpenSSH server instance service
   copy:
@@ -100,7 +100,7 @@
     dest: "/etc/default/ssh-backup"
     owner: root
     group: root
-    mode: 0644
+    mode: "0644"
   notify:
     - Restart backup SSH server
 
@@ -110,7 +110,7 @@
     dest: "/etc/ssh-backup/sshd_config"
     owner: root
     group: root
-    mode: 0600
+    mode: "0600"
   notify:
     - Restart backup SSH server
 
@@ -120,7 +120,7 @@
     dest: "/etc/ssh-backup/ssh_host_{{ item.key }}_key"
     owner: root
     group: root
-    mode: 0600
+    mode: "0600"
   with_dict: "{{ backup_host_ssh_private_keys }}"
   notify:
     - Restart backup SSH server
@@ -132,7 +132,7 @@
     dest: "/etc/systemd/system/ssh-backup.service"
     owner: root
     group: root
-    mode: 0644
+    mode: "0644"
   notify:
     - Reload systemd
     - Restart backup SSH server
@@ -149,7 +149,7 @@
     dest: "/etc/ferm/conf.d/40-backup.conf"
     owner: root
     group: root
-    mode: 0640
+    mode: "0640"
   notify:
     - Restart ferm