cannot restart bind service

I am working with Bind DNS for some dynamic ip updating concepts so i made some changes in my bind configuration /etc/named.conf file and i restarted my bind service i got some error.

[root@ns1 named]# service named restart
Stopping named: .                                          [  OK  ]
Starting named:
Error in named configuration:
/etc/named.conf:160: zone ' test.example.com' : ' allow-update'  is ignored when ' update-policy'  is present
                                                           [FAILED]