diff --git a/src/conductor/client/automator/async_task_runner.py b/src/conductor/client/automator/async_task_runner.py
index 41e7ab56..c0e601f2 100644
--- a/src/conductor/client/automator/async_task_runner.py
+++ b/src/conductor/client/automator/async_task_runner.py
@@ -841,11 +841,12 @@ async def __async_update_task(self, task_result: TaskResult):
                     )
                     return None
             except ApiException as e:
-                if e.status == 404 and self._use_update_v2:
+                if e.status in (404, 405) and self._use_update_v2:
                     logger.warning(
-                        "Server does not support update-task-v2 endpoint (HTTP 404). "
+                        "Server does not support update-task-v2 endpoint (HTTP %d). "
                         "Falling back to v1 update endpoint. "
-                        "Upgrade your Conductor instance to v5+ to enable the v2 endpoint."
+                        "Upgrade your Conductor instance to v5+ to enable the v2 endpoint.",
+                        e.status,
                     )
                     self._use_update_v2 = False
                     # Retry immediately with v1
diff --git a/src/conductor/client/automator/task_runner.py b/src/conductor/client/automator/task_runner.py
index 7168edf5..dbc97f18 100644
--- a/src/conductor/client/automator/task_runner.py
+++ b/src/conductor/client/automator/task_runner.py
@@ -871,11 +871,12 @@ def __update_task(self, task_result: TaskResult):
                     )
                     return None
             except ApiException as e:
-                if e.status == 404 and self._use_update_v2:
+                if e.status in (404, 405) and self._use_update_v2:
                     logger.warning(
-                        "Server does not support update-task-v2 endpoint (HTTP 404). "
+                        "Server does not support update-task-v2 endpoint (HTTP %d). "
                         "Falling back to v1 update endpoint. "
-                        "Upgrade your Orkes instance to v5+ to enable the v2 endpoint."
+                        "Upgrade your Orkes instance to v5+ to enable the v2 endpoint.",
+                        e.status,
                     )
                     self._use_update_v2 = False
                     # Retry immediately with v1
diff --git a/tests/unit/automator/test_task_runner_coverage.py b/tests/unit/automator/test_task_runner_coverage.py
index d7b0ba91..e2d474bf 100644
--- a/tests/unit/automator/test_task_runner_coverage.py
+++ b/tests/unit/automator/test_task_runner_coverage.py
@@ -829,6 +829,29 @@ def test_update_task_v2_404_falls_back_to_v1(self):
         mock_v1.assert_called_once()
         self.assertIsNone(result)
 
+    @patch('time.sleep', Mock(return_value=None))
+    def test_update_task_v2_405_falls_back_to_v1(self):
+        """When server returns 405 for v2 endpoint (older Conductor), should fall back to v1."""
+        worker = MockWorker('test_task')
+        task_runner = TaskRunner(worker=worker)
+
+        task_result = TaskResult(
+            task_id='test_id',
+            workflow_instance_id='wf_id',
+            worker_id=worker.get_identity(),
+            status=TaskResultStatus.COMPLETED
+        )
+
+        with patch.object(TaskResourceApi, 'update_task_v2',
+                          side_effect=ApiException(status=405)) as mock_v2, \
+             patch.object(TaskResourceApi, 'update_task', return_value='ok') as mock_v1:
+            result = task_runner._TaskRunner__update_task(task_result)
+
+        mock_v2.assert_called_once()
+        mock_v1.assert_called_once()
+        self.assertIsNone(result)
+        self.assertFalse(task_runner._use_update_v2)
+
     @patch('time.sleep', Mock(return_value=None))
     def test_update_task_v2_404_sets_v1_flag(self):
         """After a 404 on v2, _use_update_v2 flag must be False."""