diff --git a/waybackpy/wrapper.py b/waybackpy/wrapper.py
index 24cd800..30bbc59 100644
--- a/waybackpy/wrapper.py
+++ b/waybackpy/wrapper.py
@@ -80,7 +80,7 @@ class Url:
         return "%s" % self.archive_url
 
     def __len__(self):
-        if self.timestamp is None:
+        if type(self.timestamp) is None:
             return None
         else
             diff = datetime.utcnow() - self.timestamp