diff --git a/oslo_versionedobjects/fixture.py b/oslo_versionedobjects/fixture.py
index 9c1925a..407b908 100644
--- a/oslo_versionedobjects/fixture.py
+++ b/oslo_versionedobjects/fixture.py
@@ -265,8 +265,8 @@ class ObjectVersionChecker(object):
                 obj_name, extra_data_func=extra_data_func)
         return fingerprints
 
-    def test_hashes(self, expected_hashes):
-        fingerprints = self.get_hashes()
+    def test_hashes(self, expected_hashes, extra_data_func=None):
+        fingerprints = self.get_hashes(extra_data_func=extra_data_func)
 
         stored = set(expected_hashes.items())
         computed = set(fingerprints.items())
diff --git a/oslo_versionedobjects/tests/test_fixture.py b/oslo_versionedobjects/tests/test_fixture.py
index 46effce..bd564da 100644
--- a/oslo_versionedobjects/tests/test_fixture.py
+++ b/oslo_versionedobjects/tests/test_fixture.py
@@ -322,6 +322,16 @@ class TestObjectVersionChecker(test.TestCase):
                          "should contain the updated object with the new "
                          "hash.")
 
+    def test_test_hashes_passes_extra_func(self):
+        # Make sure that test_hashes passes the extra_func to get_hashes
+        mock_extra_func = mock.Mock()
+
+        with mock.patch.object(self.ovc, 'get_hashes') as mock_get_hashes:
+            self.ovc.test_hashes({}, extra_data_func=mock_extra_func)
+
+            mock_get_hashes.assert_called_once_with(
+                extra_data_func=mock_extra_func)
+
     def test_get_dependency_tree(self):
         # Make sure get_dependency_tree() gets the dependencies of all
         # objects in the registry