diff --git a/kbcstorage/base.py b/kbcstorage/base.py
index d2af4f2..8290e79 100644
--- a/kbcstorage/base.py
+++ b/kbcstorage/base.py
@@ -134,6 +134,5 @@ def _extend(self, base, parts):
             joined (:obj:`str`): The parts joined to base by forward slash,
                 eg. 'http://example.com/hello/a/deeper/path'.
         """
-        parts.insert(0, base)
-        return '/'.join([str(part).strip('/') for part in parts if
-                         str(part).strip('/')])
+        return '/'.join([base, *[str(part).strip('/') for part in parts if
+                         str(part).strip('/')]])