diff --git a/confluent_server/confluent/messages.py b/confluent_server/confluent/messages.py
index 67c914c9..9245d38a 100644
--- a/confluent_server/confluent/messages.py
+++ b/confluent_server/confluent/messages.py
@@ -623,7 +623,7 @@ def checkaccess(user, filename, pwent):
         return False
 
 def isurl(value):
-    prefix, value = value.split('://', 1) if '://' in value else (None, value)
+    prefix, value = value.split('://', 1) if '://' in value else ('', value)
     if '/' in prefix:
         return False
     return True if prefix else False