diff --git a/doc/source/developer-docs/inventory.rst b/doc/source/developer-docs/inventory.rst
index ad641b5b1c..6080363987 100644
--- a/doc/source/developer-docs/inventory.rst
+++ b/doc/source/developer-docs/inventory.rst
@@ -35,12 +35,17 @@ This invocation is useful when testing changes to the dynamic inventory script.
 Inputs
 ^^^^^^
 
-The ``dynamic_inventory.py`` script takes a single argument, ``--config``. If
-not specified, the default is ``/etc/openstack_deploy/``.
+The ``dynamic_inventory.py`` takes the ``--config`` argument for the directory
+holding configuration from which to create the inventory. If not specified,
+the default is ``/etc/openstack_deploy/``.
 
 In addition to this argument, the base environment skeleton is provided in the
 ``playbooks/inventory/env.d`` directory of the OpenStack-Ansible codebase.
 
+Should an ``env.d`` directory be found in the directory specified by
+``--config``, it's contents will be added to the base environment, overriding
+any previous contents in the event of conflicts.
+
 .. note:: In all versions prior to |previous_release_formal_name|, this argument was ``--file``.
 
 The following file must be present in the configuration directory:
@@ -101,6 +106,17 @@ The same JSON structure is printed to stdout, which is consumed by Ansible as
 the inventory for the playbooks.
 
 
+Changing the Base Environment Directory
+---------------------------------------
+
+The ``--environment/-e`` argument will take the path to a directory containing
+an ``env.d`` directory. This defaults to ``playbooks/inventory/`` in the
+OpenStack-Ansible codebase.
+
+Contents of this directory are populated into the environment *before* the
+``env.d`` found in the directory specified by ``--config``.
+
+
 Checking Inventory Configuration for Errors
 -------------------------------------------
 
diff --git a/playbooks/inventory/dynamic_inventory.py b/playbooks/inventory/dynamic_inventory.py
index fa0649715b..297fd35591 100755
--- a/playbooks/inventory/dynamic_inventory.py
+++ b/playbooks/inventory/dynamic_inventory.py
@@ -158,6 +158,15 @@ def args(arg_list):
         default=False,
     )
 
+    parser.add_argument(
+        '-e',
+        '--environment',
+        help=('Directory that contains the base env.d directory.\n'
+              'Defaults to <OSA_ROOT>/playbooks/inventory/.'),
+        required=False,
+        default=os.path.dirname(__file__),
+    )
+
     return vars(parser.parse_args(arg_list))
 
 
@@ -1166,7 +1175,7 @@ def get_inventory(config_path, inventory_file_path):
     return dynamic_inventory
 
 
-def main(config=None, check=False, debug=False, **kwargs):
+def main(config=None, check=False, debug=False, environment=None, **kwargs):
     """Run the main application.
 
     :param config: ``str`` Directory from which to pull configs and overrides
@@ -1175,6 +1184,7 @@ def main(config=None, check=False, debug=False, **kwargs):
     :param kwargs: ``dict`` Dictionary of arbitrary arguments; mostly for
         catching Ansible's required `--list` parameter without name shadowing
         the `list` built-in.
+    :param environment: ``str`` Directory containing the base env.d
     """
     if debug:
         log_fmt = "%(lineno)d - %(funcName)s: %(message)s"
@@ -1188,8 +1198,8 @@ def main(config=None, check=False, debug=False, **kwargs):
     )
 
     user_defined_config = load_user_configuration(config_path)
-
-    base_env = load_environment(os.path.dirname(__file__), {})
+    base_env_dir = environment
+    base_env = load_environment(base_env_dir, {})
     environment = load_environment(config_path, base_env)
 
     # Load existing inventory file if found
diff --git a/tests/test_inventory.py b/tests/test_inventory.py
index a0d9b64a81..5e055e84cf 100644
--- a/tests/test_inventory.py
+++ b/tests/test_inventory.py
@@ -91,7 +91,8 @@ def get_inventory(clean=True, extra_args=None):
     "Return the inventory mapping in a dict."
     # Use the list argument to more closely mirror
     # Ansible's use of the callable.
-    args = {'config': TARGET_DIR, 'list': True}
+    args = {'config': TARGET_DIR, 'list': True,
+            'environment': BASE_ENV_DIR}
     if extra_args:
         args.update(extra_args)
     try:
@@ -1108,14 +1109,15 @@ class TestConfigCheckFunctional(TestConfigCheckBase):
         self.user_defined_config['log_hosts']['bogus'] = ip
 
     def test_checking_good_config(self):
-        output = di.main(config=TARGET_DIR, check=True)
+        output = di.main(config=TARGET_DIR, check=True,
+                         environment=BASE_ENV_DIR)
         self.assertEqual(output, 'Configuration ok!')
 
     def test_duplicated_ip(self):
         self.duplicate_ip()
         self.write_config()
         with self.assertRaises(di.MultipleHostsWithOneIPError) as context:
-            di.main(config=TARGET_DIR, check=True)
+            di.main(config=TARGET_DIR, check=True, environment=BASE_ENV_DIR)
         self.assertEqual(context.exception.ip, '172.29.236.100')