diff --git a/plugin.py b/plugin.py
index 9c62d19..6878283 100644
--- a/plugin.py
+++ b/plugin.py
@@ -57,7 +57,7 @@ except ImportError:
 	try:
 		from netaddr import IPAddress, IPNetwork
 	except:
-		t = ''
+		print 'CIDR computation is not available: netaddress or ipaddress must be installed'
 
 #due to more kind of pattern checked, increase size