diff --git a/netbox_zabbix_sync.py b/netbox_zabbix_sync.py
index d4d3577..0d2d84d 100755
--- a/netbox_zabbix_sync.py
+++ b/netbox_zabbix_sync.py
@@ -207,10 +207,11 @@ class NetworkDevice():
             self.hg_format = []
             for curr_part in parts:
                 if curr_part in self._hg_map:
-                    val = rgetattr(self.nb, curr_part, 'Unknown')
-                    if val == 'Unknown':
+                    val = rgetattr(self.nb, curr_part)
+                    if val == None:
                         logger.error("Value of '{0}' is not set on host '{1}'".\
                             format(curr_part, self.name))
+                        val = 'Unknown'
                     self.hg_format.append(str(val))
                 else:
                     logger.error("Unknown field specifier: {0}".\