--- a/pvl/dns/zone.py	Tue Dec 17 00:59:56 2013 +0200
+++ b/pvl/dns/zone.py	Tue Dec 17 01:01:10 2013 +0200
@@ -615,7 +615,7 @@
         octets = octets[-int(math.ceil(hostbits / 8.0)):]
         
         # reverse in decimal
-        return '.'.join(reversed(["{0:d}".format() for x in octets]))
+        return '.'.join(reversed(["{0:d}".format(x) for x in octets]))
 
     elif prefix.version == 6 :
         # pack into nibbles