diff --git a/neutron/tests/unit/agent/linux/test_async_process.py b/neutron/tests/unit/agent/linux/test_async_process.py
index 6e72061723f..43ae302a27c 100644
--- a/neutron/tests/unit/agent/linux/test_async_process.py
+++ b/neutron/tests/unit/agent/linux/test_async_process.py
@@ -291,4 +291,7 @@ class TestFailingAsyncProcess(base.BaseTestCase):
                 as handle_error_mock:
             self.process.start()
             self.process._process.wait()
+            # Wait for the monitor process to complete
+            for thread in self.process._watchers:
+                thread.wait()
             self.assertEqual(1, handle_error_mock.call_count)