diff --git a/coriolis/conductor/rpc/client.py b/coriolis/conductor/rpc/client.py
index e8d539c2..9a2a12b0 100644
--- a/coriolis/conductor/rpc/client.py
+++ b/coriolis/conductor/rpc/client.py
@@ -294,7 +294,10 @@ def add_task_progress_update(
     def update_task_progress_update(
             self, ctxt, task_id, progress_update_index, new_current_step,
             new_total_steps=None, new_message=None):
-        self._cast(
+        # Must use synchronous RPC: EventManager advances last_perc only after
+        # this returns; fire-and-forget can lose the final update while state
+        # has already moved on, preventing any retry.
+        return self._call(
             ctxt, 'update_task_progress_update', task_id=task_id,
             progress_update_index=progress_update_index,
             new_current_step=new_current_step,
diff --git a/coriolis/tests/conductor/rpc/test_client.py b/coriolis/tests/conductor/rpc/test_client.py
index 2fc6084b..11d27100 100644
--- a/coriolis/tests/conductor/rpc/test_client.py
+++ b/coriolis/tests/conductor/rpc/test_client.py
@@ -291,8 +291,7 @@ def test_update_task_progress_update(self):
             "new_total_steps": None,
             "new_message": None
         }
-        self._test(self.client.update_task_progress_update, args,
-                   rpc_op='_cast')
+        self._test(self.client.update_task_progress_update, args)
 
     def test_create_transfer_schedule(self):
         args = {