configure name_servers only if defined
diff --git a/isc_dhcp/files/dhcpd.conf b/isc_dhcp/files/dhcpd.conf
index d0f93d2..61419f7 100644
--- a/isc_dhcp/files/dhcpd.conf
+++ b/isc_dhcp/files/dhcpd.conf
@@ -74,8 +74,9 @@
 {%- endif %}
 
 option domain-name "{{ server.domain_name }}";
+{%- if server.name_servers is defined %}
 option domain-name-servers {{ server.name_servers|join( ', ') }};
-
+{%- endif %}
 allow booting;
 allow bootp;