diff --git a/tests/integration/_support/process.py b/tests/integration/_support/process.py
index 8e9f689ec2d..12780540380 100644
--- a/tests/integration/_support/process.py
+++ b/tests/integration/_support/process.py
@@ -119,7 +119,7 @@ def _stop(process: subprocess.Popen[bytes]) -> None:
 
 
 _PORT_ATTEMPTS: Final = 3
-_BIND_COLLISION: Final = os.strerror(errno.EADDRINUSE)
+_BIND_COLLISION: Final = os.strerror(errno.EADDRINUSE).lower()
 
 
 def _free_port() -> int:
@@ -151,7 +151,7 @@ def _launch(command: tuple[str, ...], root: Path, environment: Mapping[str, str]
 
 
 def _lost_port_race(exit_code: int | None, log: Path) -> bool:
-    return exit_code is not None and _BIND_COLLISION in log.read_text()
+    return exit_code is not None and _BIND_COLLISION in log.read_text().lower()
 
 
 def _wait_until_ready(launch: _Launch) -> None:
diff --git a/tests/unit/integration_support/test_process.py b/tests/unit/integration_support/test_process.py
index 042a2447dff..7896786fce8 100644
--- a/tests/unit/integration_support/test_process.py
+++ b/tests/unit/integration_support/test_process.py
@@ -1,8 +1,10 @@
 from __future__ import annotations
 
+import asyncio
 import errno
 import importlib
-import os
+import socket
+from collections.abc import Iterator
 from pathlib import Path
 from types import ModuleType
 from typing import Final
@@ -10,7 +12,6 @@ from typing import Final
 import pytest
 
 TESTS_DIR: Final = Path(__file__).resolve().parents[2]
-BIND_ERROR_LINE: Final = f"ERROR:    {OSError(errno.EADDRINUSE, os.strerror(errno.EADDRINUSE))}\n"
 UNRELATED_CRASH: Final = "Traceback (most recent call last):\nModuleNotFoundError: No module named 'litellm'\n"
 
 
@@ -20,19 +21,41 @@ def process_module(monkeypatch: pytest.MonkeyPatch) -> ModuleType:
     return importlib.import_module("integration._support.process")
 
 
+async def _refused_bind(port: int) -> OSError | None:
+    try:
+        await asyncio.get_running_loop().create_server(asyncio.Protocol, "127.0.0.1", port)
+    except OSError as refused:
+        return refused
+    return None
+
+
+@pytest.fixture
+def bind_error_line() -> Iterator[str]:
+    with socket.socket() as held:
+        held.bind(("127.0.0.1", 0))
+        held.listen()
+        refused: Final = asyncio.run(_refused_bind(held.getsockname()[1]))
+        assert refused is not None and refused.errno == errno.EADDRINUSE
+        yield f"ERROR:    {refused}\n"
+
+
 def _written_log(directory: Path, text: str) -> Path:
     log: Final = directory / "owned-proxy.log"
     log.write_text(text)
     return log
 
 
-def test_lost_port_race_matches_the_bind_error_the_server_logs(process_module: ModuleType, tmp_path: Path) -> None:
-    assert process_module._lost_port_race(1, _written_log(tmp_path, BIND_ERROR_LINE))
+def test_lost_port_race_matches_the_bind_error_the_server_logs(
+    process_module: ModuleType, bind_error_line: str, tmp_path: Path
+) -> None:
+    assert process_module._lost_port_race(1, _written_log(tmp_path, bind_error_line))
 
 
 def test_lost_port_race_ignores_an_exit_for_another_reason(process_module: ModuleType, tmp_path: Path) -> None:
     assert not process_module._lost_port_race(1, _written_log(tmp_path, UNRELATED_CRASH))
 
 
-def test_lost_port_race_needs_the_process_to_have_exited(process_module: ModuleType, tmp_path: Path) -> None:
-    assert not process_module._lost_port_race(None, _written_log(tmp_path, BIND_ERROR_LINE))
+def test_lost_port_race_needs_the_process_to_have_exited(
+    process_module: ModuleType, bind_error_line: str, tmp_path: Path
+) -> None:
+    assert not process_module._lost_port_race(None, _written_log(tmp_path, bind_error_line))