diff --git a/devapp/models.py b/devapp/models.py
index 210047d..dd75d53 100644
--- a/devapp/models.py
+++ b/devapp/models.py
@@ -88,7 +88,7 @@ class Device(models.Model):
 
     def update_dhcp(self):
         from .onu_register import onu_register
-        onu_register(self.objects.exclude(group=None).iterator())
+        onu_register(Device.objects.exclude(group=None).select_related('group').only('mac_addr', 'group__code').iterator())
 
     def generate_config_template(self) -> Optional[AnyStr]:
         mng = self.get_manager_object()
diff --git a/devapp/onu_register.py b/devapp/onu_register.py
index 0ab6ec6..71b3f60 100644
--- a/devapp/onu_register.py
+++ b/devapp/onu_register.py
@@ -6,7 +6,7 @@ from subprocess import run
 def onu_register(devices: Iterable):
     with open('/etc/dhcp/macs.conf', 'w') as f:
         for dev in devices:
-            if dev.has_attachable_to_subscriber():
+            if dev.has_attachable_to_subscriber() and dev.mac_addr is not None:
                 f.write('subclass "%(code)s" "%(mac)s";\n' % {
                     'code': dev.group.code,
                     'mac': dev.mac_addr