diff --git a/tests/hermes_cli/test_gateway.py b/tests/hermes_cli/test_gateway.py
index 0a44ac9532..6dfbd636f4 100644
--- a/tests/hermes_cli/test_gateway.py
+++ b/tests/hermes_cli/test_gateway.py
@@ -310,6 +310,10 @@ def test_find_gateway_pids_falls_back_to_pid_file_when_process_scan_fails(monkey
     def fake_run(cmd, **kwargs):
         if cmd[:4] == ["ps", "-A", "eww", "-o"]:
             return SimpleNamespace(returncode=1, stdout="", stderr="ps failed")
+        if cmd[:3] == ["ps", "-o", "ppid="]:
+            # _get_ancestor_pids() walks up the tree; return "no parent" so
+            # the loop terminates cleanly.
+            return SimpleNamespace(returncode=1, stdout="", stderr="")
         raise AssertionError(f"Unexpected command: {cmd}")
 
     monkeypatch.setattr(gateway.subprocess, "run", fake_run)