diff --git a/conf/systemd.service b/conf/systemd.service
index bdc4a9d..01f146d 100644
--- a/conf/systemd.service
+++ b/conf/systemd.service
@@ -16,7 +16,7 @@ ExecStart=/bin/sh -c '__INSTALL_DIR__/venv/bin/python3 __INSTALL_DIR__/cps.py'
 NoNewPrivileges=yes
 PrivateTmp=yes
 PrivateDevices=yes
-RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6 AF_NETLINK
 RestrictNamespaces=yes
 RestrictRealtime=yes
 DevicePolicy=closed
diff --git a/doc/PRE_UPGRADE.d/0.96.21~ynh2.md b/doc/PRE_UPGRADE.d/0.96.21~ynh2.md
new file mode 100644
index 0000000..44d7d22
--- /dev/null
+++ b/doc/PRE_UPGRADE.d/0.96.21~ynh2.md
@@ -0,0 +1 @@
+This version will fix downloading of book covers from external links.
\ No newline at end of file