diff --git a/src/sipcentric/__init__.py b/src/sipcentric/__init__.py
index 25c4c9e..fc6bcf0 100644
--- a/src/sipcentric/__init__.py
+++ b/src/sipcentric/__init__.py
@@ -189,7 +189,7 @@ class APIObject(object):
         else:
             path = "/%s/" % (cls.URLPART)
         if parent:
-            return (parent + path).replace("//", "/")
+            return (parent.url() + path).replace("//", "/")
         return path
 
     def url(self, parent=None):