diff --git a/tests/integration/mcp/test_mcp_credentials.py b/tests/integration/mcp/test_mcp_credentials.py
index 95a5e46646b..b3f5725040a 100644
--- a/tests/integration/mcp/test_mcp_credentials.py
+++ b/tests/integration/mcp/test_mcp_credentials.py
@@ -192,3 +192,26 @@ def test_byok_server_uses_the_calling_users_stored_credential_and_fails_closed_w
         assert removed.status_code in (200, 204), removed.text
         eventually(lambda: call_tool(gateway, owner_key, identity, name, ADD), lambda value: value.status_code == 401)
         assert tool_calls(peer.drain()) == ()
+
+
+def test_deprecated_string_x_mcp_auth_lists_a_byok_server_for_a_key_without_a_user(gateway: Gateway) -> None:
+    with mcp_peer() as peer, gateway.scenario() as scenario:
+        alias: Final = "byok" + uuid.uuid4().hex[:8]
+        identity: Final = register_mcp(scenario, peer, alias, auth_type="bearer_token", is_byok=True)
+        key: Final = scenario.key(object_permission={"mcp_servers": [identity]})
+        peer.drain()
+        response: Final = gateway.client.get(
+            "/mcp-rest/tools/list",
+            params={"server_id": identity},
+            headers={"x-litellm-api-key": key, "x-mcp-auth": "Bearer hdr"},
+        )
+        assert response.status_code == 200, response.text
+        names: Final = {tool["name"] for tool in response.json()["tools"]}
+        assert "add" in names, names
+        listings: Final = tuple(
+            item
+            for item in peer.drain()
+            if isinstance(item.get("body"), dict) and item["body"].get("method") == "tools/list"
+        )
+        assert len(listings) == 1, listings
+        assert listings[0]["headers"].get(b"authorization") == b"Bearer hdr"