diff --git a/playbooks/tasks/upgrade-servers.yml b/playbooks/tasks/upgrade-servers.yml
index 100a84f2c6a420d8a1c797b6e54709faf82f235d..75b7836fbd4092b3816561683e639ed81418757a 100644
--- a/playbooks/tasks/upgrade-servers.yml
+++ b/playbooks/tasks/upgrade-servers.yml
@@ -2,6 +2,7 @@
 
 - name: upgrade and reboot all servers
   hosts: all,!rsync_net,!hetzner_storageboxes
+  serial: 20%
   gather_facts: false
 
   tasks: