dhcpd fails to start because "no option named XXX in space dhcp"

Issue

dhcpd service fails to start because of the configuration file error encountered:
no option named arch in space dhcp

# systemctl status dhcpd.service
● dhcpd.service - DHCPv4 Server Daemon
   Loaded: loaded (/usr/lib/systemd/system/dhcpd.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Fri 2018-10-05 14:16:59 CEST; 14s ago
     Docs: man:dhcpd(8)
           man:dhcpd.conf(5)
  Process: 28204 ExecStart=/usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid (code=exited, status=1/FAILURE)
 Main PID: 28204 (code=exited, status=1/FAILURE)

Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]: /etc/dhcp/dhcpd.conf line 22: no option named arch in space dhcp
Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]: if option arch  =
Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]:            ^
Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]: Configuration file errors encountered -- exiting
Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]: 
Oct 05 14:16:59 rhel-7-5-75 dhcpd[28204]: This version of ISC DHCP is based on the release available
Oct 05 14:16:59 rhel-7-5-75 systemd[1]: dhcpd.service: main process exited, code=exited, status=1/FAILURE
Oct 05 14:16:59 rhel-7-5-75 systemd[1]: Failed to start DHCPv4 Server Daemon.
Oct 05 14:16:59 rhel-7-5-75 systemd[1]: Unit dhcpd.service entered failed state.
Oct 05 14:16:59 rhel-7-5-75 systemd[1]: dhcpd.service failed.