diff --git a/containers/zammad-postgresql/backup.sh b/containers/zammad-postgresql/backup.sh
index 02cf4b4..f27f8e3 100644
--- a/containers/zammad-postgresql/backup.sh
+++ b/containers/zammad-postgresql/backup.sh
@@ -3,9 +3,10 @@
 set -e
 
 : "${ZAMMAD_RAILSSERVER_HOST:=zammad-railsserver}"
+: "${ZAMMAD_RAILSSERVER_PORT:=3000}"
 
 function check_railsserver_available {
-  until (echo > /dev/tcp/${ZAMMAD_RAILSSERVER_HOST}/3000) &> /dev/null; do
+  until (echo > /dev/tcp/${ZAMMAD_RAILSSERVER_HOST}/${ZAMMAD_RAILSSERVER_PORT}) &> /dev/null; do
     echo "waiting for railsserver to be ready..."
     sleep 60
   done