--- a/pvl/hosts/zone.py	Wed Feb 25 15:40:58 2015 +0200
+++ b/pvl/hosts/zone.py	Wed Feb 25 15:49:11 2015 +0200
@@ -179,6 +179,9 @@
 
         Yields ZoneRecords in IPAddress-order
     """
+        
+    if options.unknown_host and not options.hosts_domain:
+        raise Exception("--unknown-host requires --hosts-domain")
     
     # collect data for records
     by_ip = dict()
@@ -204,13 +207,13 @@
         elif options.unknown_host:
             # synthesize a record
             label = pvl.dns.reverse_label(prefix, ip)
-            fqdn = pvl.dns.zone.fqdn(options.unknown_host, options.hosts_domain)
+            fqdn = pvl.dns.fqdn(options.unknown_host, options.hosts_domain)
 
             log.info("%s %s[%s]: unused PTR %s", options.unknown_host, ip, prefix, fqdn)
 
-            yield pvl.dns.zone.ZoneRecord.PTR(label, fqdn)
+            yield pvl.dns.ZoneRecord.PTR(label, fqdn)
 
-        else :
+        else:
             continue
 
 import pvl.args