diff --git a/src/documents/tests/test_api_document_versions.py b/src/documents/tests/test_api_document_versions.py
index 34228b209..8f5465357 100644
--- a/src/documents/tests/test_api_document_versions.py
+++ b/src/documents/tests/test_api_document_versions.py
@@ -465,6 +465,39 @@ class TestDocumentVersioningApi(DirectoriesMixin, APITestCase):
         self.assertEqual(overrides.version_label, "New Version")
         self.assertEqual(overrides.actor_id, self.user.id)
 
+    def test_update_version_with_version_pk_normalizes_to_root(self) -> None:
+        root = Document.objects.create(
+            title="root",
+            checksum="root",
+            mime_type="application/pdf",
+        )
+        version = Document.objects.create(
+            title="v1",
+            checksum="v1",
+            mime_type="application/pdf",
+            root_document=root,
+        )
+        upload = self._make_pdf_upload()
+
+        async_task = mock.Mock()
+        async_task.id = "task-123"
+
+        with mock.patch("documents.views.consume_file") as consume_mock:
+            consume_mock.delay.return_value = async_task
+            resp = self.client.post(
+                f"/api/documents/{version.id}/update_version/",
+                {"document": upload, "version_label": "  New Version  "},
+                format="multipart",
+            )
+
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        self.assertEqual(resp.data, "task-123")
+        consume_mock.delay.assert_called_once()
+        input_doc, overrides = consume_mock.delay.call_args[0]
+        self.assertEqual(input_doc.root_document_id, root.id)
+        self.assertEqual(overrides.version_label, "New Version")
+        self.assertEqual(overrides.actor_id, self.user.id)
+
     def test_update_version_returns_500_on_consume_failure(self) -> None:
         root = Document.objects.create(
             title="root",
diff --git a/src/documents/views.py b/src/documents/views.py
index 2cbcf9726..58529b920 100644
--- a/src/documents/views.py
+++ b/src/documents/views.py
@@ -1573,11 +1573,15 @@ class DocumentViewSet(
         serializer.is_valid(raise_exception=True)
 
         try:
-            doc = Document.objects.select_related("owner").get(pk=pk)
+            request_doc = Document.objects.select_related(
+                "owner",
+                "root_document",
+            ).get(pk=pk)
+            root_doc = get_root_document(request_doc)
             if request.user is not None and not has_perms_owner_aware(
                 request.user,
                 "change_document",
-                doc,
+                root_doc,
             ):
                 return HttpResponseForbidden("Insufficient permissions")
         except Document.DoesNotExist:
@@ -1602,7 +1606,7 @@ class DocumentViewSet(
             input_doc = ConsumableDocument(
                 source=DocumentSource.ApiUpload,
                 original_file=temp_file_path,
-                root_document_id=doc.pk,
+                root_document_id=root_doc.pk,
             )
 
             overrides = DocumentMetadataOverrides()
@@ -1616,7 +1620,7 @@ class DocumentViewSet(
                 overrides,
             )
             logger.debug(
-                f"Updated document {doc.id} with new version",
+                f"Updated document {root_doc.id} with new version",
             )
             return Response(async_task.id)
         except Exception as e: