diff --git a/.github/workflows/cygwin-test.yml b/.github/workflows/cygwin-test.yml
index b612ca94a..808dc5608 100644
--- a/.github/workflows/cygwin-test.yml
+++ b/.github/workflows/cygwin-test.yml
@@ -46,8 +46,4 @@ jobs:
       shell: bash.exe -eo pipefail -o igncr "{0}"
       run: |
         /usr/bin/python -m pytest
-      env:
-        GIT_CONFIG_COUNT: "1"
-        GIT_CONFIG_KEY_0: protocol.file.allow
-        GIT_CONFIG_VALUE_0: always
       continue-on-error: false
diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index 207714810..a6af507d1 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -56,10 +56,6 @@ jobs:
       run: |
         set -x
         pytest
-      env:
-        GIT_CONFIG_COUNT: "1"
-        GIT_CONFIG_KEY_0: protocol.file.allow
-        GIT_CONFIG_VALUE_0: always
       continue-on-error: false
 
     - name: Documentation
diff --git a/test/test_submodule.py b/test/test_submodule.py
index 982226411..aeb6f746a 100644
--- a/test/test_submodule.py
+++ b/test/test_submodule.py
@@ -1,12 +1,13 @@
 # -*- coding: utf-8 -*-
 # This module is part of GitPython and is released under
 # the BSD License: http://www.opensource.org/licenses/bsd-license.php
+import contextlib
 import os
 import shutil
 import tempfile
 from pathlib import Path
 import sys
-from unittest import skipIf
+from unittest import mock, skipIf
 
 import pytest
 
@@ -31,6 +32,23 @@
 import os.path as osp
 
 
+@contextlib.contextmanager
+def _allow_file_protocol():
+    """Temporarily set protocol.file.allow to always, using environment variables."""
+    pair_index = int(os.getenv("GIT_CONFIG_COUNT", "0"))
+
+    # This is recomputed each time the context is entered, for compatibility with
+    # existing GIT_CONFIG_* environment variables, even if changed in this process.
+    patcher = mock.patch.dict(os.environ, {
+        "GIT_CONFIG_COUNT": str(pair_index + 1),
+        f"GIT_CONFIG_KEY_{pair_index}": "protocol.file.allow",
+        f"GIT_CONFIG_VALUE_{pair_index}": "always",
+    })
+
+    with patcher:
+        yield
+
+
 class TestRootProgress(RootUpdateProgress):
     """Just prints messages, for now without checking the correctness of the states"""
 
@@ -709,6 +727,7 @@ def test_add_empty_repo(self, rwdir):
         # end for each checkout mode
 
     @with_rw_directory
+    @_allow_file_protocol
     def test_list_only_valid_submodules(self, rwdir):
         repo_path = osp.join(rwdir, "parent")
         repo = git.Repo.init(repo_path)
@@ -737,6 +756,7 @@ def test_list_only_valid_submodules(self, rwdir):
                 """,
     )
     @with_rw_directory
+    @_allow_file_protocol
     def test_git_submodules_and_add_sm_with_new_commit(self, rwdir):
         parent = git.Repo.init(osp.join(rwdir, "parent"))
         parent.git.submodule("add", self._small_repo_url(), "module")