diff --git a/stix2/base.py b/stix2/base.py
index a1229ca..ef3fcb8 100644
--- a/stix2/base.py
+++ b/stix2/base.py
@@ -401,25 +401,25 @@ class _Observable(_STIXBase):
 
         properties_to_use = self._id_contributing_properties
         if properties_to_use:
-            streamlined_obj_vals = []
+            streamlined_object = {}
             if "hashes" in kwargs and "hashes" in properties_to_use:
                 possible_hash = _choose_one_hash(kwargs["hashes"])
                 if possible_hash:
-                    streamlined_obj_vals.append(possible_hash)
+                    streamlined_object["hashes"] = possible_hash
             for key in properties_to_use:
                 if key != "hashes" and key in kwargs:
                     if isinstance(kwargs[key], dict) or isinstance(kwargs[key], _STIXBase):
                         temp_deep_copy = copy.deepcopy(dict(kwargs[key]))
                         _recursive_stix_to_dict(temp_deep_copy)
-                        streamlined_obj_vals.append(temp_deep_copy)
+                        streamlined_object[key] = temp_deep_copy
                     elif isinstance(kwargs[key], list):
                         temp_deep_copy = copy.deepcopy(kwargs[key])
                         _recursive_stix_list_to_dict(temp_deep_copy)
-                        streamlined_obj_vals.append(temp_deep_copy)
+                        streamlined_object[key] = temp_deep_copy
                     else:
-                        streamlined_obj_vals.append(kwargs[key])
-            if streamlined_obj_vals:
-                data = canonicalize(streamlined_obj_vals, utf8=False)
+                        streamlined_object[key] = kwargs[key]
+            if streamlined_object:
+                data = canonicalize(streamlined_object, utf8=False)
 
                 # The situation is complicated w.r.t. python 2/3 behavior, so
                 # I'd rather not rely on particular exceptions being raised to
diff --git a/stix2/properties.py b/stix2/properties.py
index 060d9ca..a1bab6d 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -503,7 +503,7 @@ class ReferenceProperty(Property):
             if possible_prefix not in ref_invalid_types:
                 required_prefix = possible_prefix
             else:
-                raise ValueError("An invalid type-specifying prefix '%s' was specified for this property" % (possible_prefix, value))
+                raise ValueError("An invalid type-specifying prefix '%s' was specified for this property" % (possible_prefix))
 
         _validate_id(value, self.spec_version, required_prefix)
 
diff --git a/stix2/test/v21/test_observed_data.py b/stix2/test/v21/test_observed_data.py
index abcbb7b..b8732be 100644
--- a/stix2/test/v21/test_observed_data.py
+++ b/stix2/test/v21/test_observed_data.py
@@ -46,7 +46,7 @@ def test_observed_data_example():
         objects={
             "0": {
                 "type": "file",
-                "id": "file--5956efbb-a7b0-566d-a7f9-a202eb05c70f",
+                "id": "file--7af1312c-4402-5d2f-b169-b118d73b85c4",
                 "name": "foo.exe",
             },
         },
@@ -102,12 +102,12 @@ def test_observed_data_example_with_refs():
         objects={
             "0": {
                 "type": "file",
-                "id": "file--5956efbb-a7b0-566d-a7f9-a202eb05c70f",
+                "id": "file--7af1312c-4402-5d2f-b169-b118d73b85c4",
                 "name": "foo.exe",
             },
             "1": {
                 "type": "directory",
-                "id": "directory--536a61a4-0934-516b-9aad-fcbb75e0583a",
+                "id": "directory--ee97f78e-7e2b-5b3d-bcbd-5692968cacea",
                 "path": "/usr/home",
                 "contains_refs": ["file--5956efbb-a7b0-566d-a7f9-a202eb05c70f"],
             },
@@ -719,7 +719,7 @@ def test_directory_example():
     assert dir1.ctime == dt.datetime(2015, 12, 21, 19, 0, 0, tzinfo=pytz.utc)
     assert dir1.mtime == dt.datetime(2015, 12, 24, 19, 0, 0, tzinfo=pytz.utc)
     assert dir1.atime == dt.datetime(2015, 12, 21, 20, 0, 0, tzinfo=pytz.utc)
-    assert dir1.contains_refs == ["file--9d050a3b-72cd-5b57-bf18-024e74e1e5eb"]
+    assert dir1.contains_refs == ["file--c6ae2cf8-92d3-56d0-a25f-713efad643a7"]
 
 
 def test_directory_example_ref_error():
@@ -747,7 +747,7 @@ def test_domain_name_example():
     )
 
     assert dn2.value == "example.com"
-    assert dn2.resolves_to_refs == ["domain-name--02af94ea-7e38-5718-87c3-5cc023e3d49d"]
+    assert dn2.resolves_to_refs == ["domain-name--5b5803bf-a7eb-5076-b799-96aa574c44eb"]
 
 
 def test_domain_name_example_invalid_ref_type():
@@ -1032,7 +1032,7 @@ def test_ipv4_address_valid_refs():
     )
 
     assert ip4.value == "177.60.40.7"
-    assert ip4.resolves_to_refs == ["mac-addr--a85820f7-d9b7-567a-a3a6-dedc34139342", "mac-addr--9a59b496-fdeb-510f-97b5-7137210bc699"]
+    assert ip4.resolves_to_refs == ["mac-addr--f72d7d00-86bd-5cd2-8c86-52f7a83bef62", "mac-addr--875ad625-177b-5c2a-9101-d44b0ad55938"]
 
 
 def test_ipv4_address_example_cidr():
@@ -1565,7 +1565,7 @@ def test_id_gen_recursive_dict_conversion_1():
         },
     )
 
-    assert file_observable.id == "file--5219d93d-13c1-5f1f-896b-039f10ec67ea"
+    assert file_observable.id == "file--ced31cd4-bdcb-537d-aefa-92d291bfc11d"
 
 
 def test_id_gen_recursive_dict_conversion_2():
@@ -1582,4 +1582,4 @@ def test_id_gen_recursive_dict_conversion_2():
         ],
     )
 
-    assert wrko.id == "windows-registry-key--c087d9fe-a03e-5922-a1cd-da116e5b8a7b"
+    assert wrko.id == "windows-registry-key--36594eba-bcc7-5014-9835-0e154264e588"