diff --git a/.idea/pySBOL3.iml b/.idea/pySBOL3.iml
index 475d9e2..a6d5897 100644
--- a/.idea/pySBOL3.iml
+++ b/.idea/pySBOL3.iml
@@ -2,6 +2,7 @@
 <module type="PYTHON_MODULE" version="4">
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$" isTestSource="false" />
       <excludeFolder url="file://$MODULE_DIR$/build" />
       <excludeFolder url="file://$MODULE_DIR$/dist" />
       <excludeFolder url="file://$MODULE_DIR$/docs/_build" />
diff --git a/sbol3/object.py b/sbol3/object.py
index 208bacd..394d1a7 100644
--- a/sbol3/object.py
+++ b/sbol3/object.py
@@ -1,9 +1,8 @@
 import posixpath
 import uuid
-import warnings
 from collections import defaultdict
 from urllib.parse import urlparse
-from typing import Dict, Callable, Optional
+from typing import Dict, Callable, Optional, Union
 
 from . import *
 
@@ -23,14 +22,14 @@ def __setattr__(self, name, value):
             self.__dict__[name].set(value)
         except AttributeError:
             # Attribute set does not exist
-            object.__setattr__(self, name, value)
+            super().__setattr__(name, value)
         except KeyError:
             # property name does not exist
-            object.__setattr__(self, name, value)
+            super().__setattr__(name, value)
 
     def __getattribute__(self, name):
         # Call the default method
-        result = object.__getattribute__(self, name)
+        result = super().__getattribute__(name)
         if hasattr(result, '_sbol_singleton'):
             result = result.get()
         return result
@@ -41,7 +40,7 @@ def _is_url(name: str) -> bool:
         return bool(parsed.scheme and parsed.netloc and parsed.path)
 
     @staticmethod
-    def _make_identity(name: str) -> str:
+    def _make_identity(name: str) -> Union[str, None]:
         """Make an identity from the given name.
 
         If the name is a URL, that can be the identity. Or perhaps it
@@ -108,18 +107,17 @@ def copy(self, target_doc=None, target_namespace=None):
                 old_uri = self.identity
                 new_uri = replace_namespace(old_uri, target_namespace, self.getTypeURI())
 
-        new_obj = BUILDER_REGISTER[self.type_uri](identity=new_uri,
-                                                  type_uri=self.type_uri)
+        new_obj = BUILDER_REGISTER[self.type_uri](**dict(identity=new_uri,
+                                                         type_uri=self.type_uri))
 
         # Copy properties
         for property_uri, value_store in self._properties.items():
             new_obj._properties[property_uri] = value_store.copy()
 
-            # TODO:
-            # Map into new namespace
+            # TODO: Map into new namespace
 
         # Assign the new object to the target Document
-        if target_doc:
+        if target_doc is not None:
             try:
                 target_doc.add(new_obj)
             except TypeError:
diff --git a/test/test_object.py b/test/test_object.py
index 2a0137b..f974d48 100644
--- a/test/test_object.py
+++ b/test/test_object.py
@@ -44,6 +44,7 @@ def test_copy_child_objects(self):
 
         doc2 = sbol3.Document()
         root_copy = root.copy(target_doc=doc2)
+        self.assertIn(root_copy, doc2.objects)
         self.assertEqual([sc.identity for sc in root.features],
                          [sc.identity for sc in root_copy.features])