diff --git a/conftest.py b/conftest.py
index fae3b7fc..77779727 100644
--- a/conftest.py
+++ b/conftest.py
@@ -34,10 +34,12 @@
 from enum import Enum
 from filecmp import cmp
 from functools import partial
+from io import BytesIO
 from pathlib import Path
 
 import jsonschema
 import pytest
+from sphinx.util.inventory import InventoryFile as IFile
 
 import sphobjinv as soi
 
@@ -161,18 +163,27 @@ def bytes_txt(misc_info, res_path):
 
 
 @pytest.fixture(scope="session")
-def sphinx_load_test():
+def sphinx_ifile_load():
+    """Return helper function to load inventory via Sphinx InventoryFile."""
+
+    def func(path):
+        """Carry out inventory load via Sphinx InventoryFile."""
+        return IFile.load(BytesIO(path.read_bytes()), "", osp.join)
+
+    return func
+
+
+@pytest.fixture(scope="session")
+def sphinx_load_test(sphinx_ifile_load):
     """Return function to perform 'live' Sphinx inventory load test."""
-    from sphinx.util.inventory import InventoryFile as IFile
 
     def func(path):
         """Perform the 'live' inventory load test."""
-        with path.open("rb") as f:
-            try:
-                IFile.load(f, "", osp.join)
-            except Exception as e:  # noqa: PIE786
-                # An exception here is a failing test, not a test error.
-                pytest.fail(e)
+        try:
+            sphinx_ifile_load(path)
+        except Exception as e:  # noqa: PIE786
+            # An exception here is a failing test, not a test error.
+            pytest.fail(e)
 
     return func
 
diff --git a/requirements-ci.txt b/requirements-ci.txt
index 27b23f9c..b07f0b60 100644
--- a/requirements-ci.txt
+++ b/requirements-ci.txt
@@ -2,6 +2,7 @@ attrs>=17.4
 certifi
 codecov
 coverage
+dictdiffer
 fuzzywuzzy>=0.3
 jsonschema
 md-toc
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 56ef758b..3e06912a 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,6 +1,7 @@
 attrs>=17.4
 certifi
 coverage
+dictdiffer
 fuzzywuzzy>=0.3
 jsonschema
 md-toc
diff --git a/tests/test_api_good.py b/tests/test_api_good.py
index e150dd2d..843ee147 100644
--- a/tests/test_api_good.py
+++ b/tests/test_api_good.py
@@ -31,6 +31,7 @@
 import warnings
 from numbers import Number
 
+import dictdiffer
 import pytest
 
 import sphobjinv as soi
@@ -502,6 +503,26 @@ def test_api_inventory_datafile_gen_and_reimport(
         # Ensure sphinx likes the regenerated inventory
         sphinx_load_test(scr_fpath)
 
+    @pytest.mark.testall
+    def test_api_inventory_matches_sphinx_ifile(
+        self, testall_inv_path, scratch_path, misc_info, pytestconfig, sphinx_ifile_load
+    ):
+        """Confirm no-op per Sphinx on passing through sphobjinv.Inventory."""
+        fname = testall_inv_path.name
+        scr_fpath = scratch_path / fname
+
+        # Drop most unless testall
+        if not pytestconfig.getoption("--testall") and fname != "objects_attrs.inv":
+            pytest.skip("'--testall' not specified")
+
+        original_ifile_data = sphinx_ifile_load(testall_inv_path)
+
+        inv = soi.Inventory(testall_inv_path)
+        soi.writebytes(scr_fpath, soi.compress(inv.data_file()))
+        soi_ifile_data = sphinx_ifile_load(scr_fpath)
+
+        assert list(dictdiffer.diff(soi_ifile_data, original_ifile_data)) == [], fname
+
     def test_api_inventory_one_object_flatdict(self):
         """Confirm a flat dict inventory with one object imports ok.