diff --git a/lib.py b/lib.py
index b6107f9..091006a 100644
--- a/lib.py
+++ b/lib.py
@@ -68,7 +68,8 @@ def get_serial(dns_zone):
     """
     Query the serial number from the NS
 
-    dns_zone can either be a str or a dns.zone.Zone obj
+    The parameter `dns_zone` can either be a `str` or a `dns.zone.Zone` object.
+    Error handling is added to return 0 if the query is unsucessful.
     """
 
     try: