diff --git a/docker/kolab/utils/07-adjust-base-dns.sh b/docker/kolab/utils/07-adjust-base-dns.sh
--- a/docker/kolab/utils/07-adjust-base-dns.sh
+++ b/docker/kolab/utils/07-adjust-base-dns.sh
@@ -21,6 +21,7 @@
     /etc/kolab-freebusy/config.ini \
     /etc/postfix/ldap/*.cf \
     /etc/roundcubemail/config.inc.php \
+    /etc/roundcubemail/calendar.inc.php \
     /etc/roundcubemail/kolab_auth.inc.php
 
 sed -i -r \