diff --git a/host_vars/unhb4/authentik.yml b/host_vars/unhb4/authentik.yml
index 5157bdc..3f14743 100644
--- a/host_vars/unhb4/authentik.yml
+++ b/host_vars/unhb4/authentik.yml
@@ -9,3 +9,4 @@ authentik_email_timeout: "10"
 authentik_port_http: "9000"
 authentik_port_https: "9443"
 authentik_domain: "auth.un-hack-bar.de,auth.unhb.de"
+authentik_allow_users_to_change_usernames: "false" # disable username changes to avoid username collisions
diff --git a/roles/authentik_docker/templates/.env.j2 b/roles/authentik_docker/templates/.env.j2
index 270fa58..8cb3f53 100644
--- a/roles/authentik_docker/templates/.env.j2
+++ b/roles/authentik_docker/templates/.env.j2
@@ -16,3 +16,4 @@ AUTHENTIK_EMAIL__TIMEOUT={{ authentik_email_timeout }}
 AUTHENTIK_EMAIL__FROM={{ authentik_email_from }}
 AUTHENTIK_PORT_HTTP={{ authentik_port_http }}
 AUTHENTIK_PORT_HTTPS={{ authentik_port_https }}
+AUTHENTIK_DEFAULT_USER_CHANGE_USERNAME={{ authentik_allow_users_to_change_usernames }}