diff --git a/tests/integration/mcp/test_mcp_lifecycle.py b/tests/integration/mcp/test_mcp_lifecycle.py
index 120fc2a5a2f..7ca5f3a69b7 100644
--- a/tests/integration/mcp/test_mcp_lifecycle.py
+++ b/tests/integration/mcp/test_mcp_lifecycle.py
@@ -7,12 +7,11 @@ import pytest
 import yaml
 from hypothesis import strategies as st
 from hypothesis.stateful import RuleBasedStateMachine, invariant, rule, run_state_machine_as_test
-
 from integration._support.client import Gateway
 from integration._support.database import read_rows
 from integration._support.generation import LIFECYCLE_SETTINGS, bounded_http_requests
-from integration._support.process import owned_proxy
 from integration._support.mcp import call_tool, mcp_peer, register_mcp, tool_names
+from integration._support.process import owned_proxy
 
 
 @pytest.mark.covers("mcp.call_tool.saved_headers.reach_actual_transport")
@@ -199,6 +198,7 @@ def test_warm_credential_removal_rejects_without_upstream_traffic(gateway: Gatew
                 else call_tool(gateway, key, identity, names["add"], {"a": 3, "b": 5})
             )
             assert rejected.status_code == 500, rejected.text
+            assert "requires a usable upstream credential" in rejected.text, rejected.text
             assert peer.drain() == (), "missing static credential escaped to upstream"
         changed = gateway.request(
             "PUT",