diff --git a/git/cmd.py b/git/cmd.py
index 3665eb029..d6f8f946a 100644
--- a/git/cmd.py
+++ b/git/cmd.py
@@ -14,7 +14,6 @@
 import subprocess
 import threading
 from textwrap import dedent
-import unittest.mock
 
 from git.compat import (
     defenc,
@@ -24,7 +23,7 @@
     is_win,
 )
 from git.exc import CommandError
-from git.util import is_cygwin_git, cygpath, expand_path, remove_password_if_present
+from git.util import is_cygwin_git, cygpath, expand_path, remove_password_if_present, patch_env
 
 from .exc import GitCommandError, GitCommandNotFound, UnsafeOptionError, UnsafeProtocolError
 from .util import (
@@ -965,10 +964,10 @@ def execute(
                     '"kill_after_timeout" feature is not supported on Windows.',
                 )
             # Only search PATH, not CWD. This must be in the *caller* environment. The "1" can be any value.
-            patch_caller_env = unittest.mock.patch.dict(os.environ, {"NoDefaultCurrentDirectoryInExePath": "1"})
+            maybe_patch_caller_env = patch_env("NoDefaultCurrentDirectoryInExePath", "1")
         else:
             cmd_not_found_exception = FileNotFoundError  # NOQA # exists, flake8 unknown @UndefinedVariable
-            patch_caller_env = contextlib.nullcontext()
+            maybe_patch_caller_env = contextlib.nullcontext()
         # end handle
 
         stdout_sink = PIPE if with_stdout else getattr(subprocess, "DEVNULL", None) or open(os.devnull, "wb")
@@ -984,7 +983,7 @@ def execute(
             istream_ok,
         )
         try:
-            with patch_caller_env:
+            with maybe_patch_caller_env:
                 proc = Popen(
                     command,
                     env=env,
diff --git a/git/util.py b/git/util.py
index f6dedf0f2..f80580cff 100644
--- a/git/util.py
+++ b/git/util.py
@@ -158,6 +158,20 @@ def cwd(new_dir: PathLike) -> Generator[PathLike, None, None]:
         os.chdir(old_dir)
 
 
+@contextlib.contextmanager
+def patch_env(name: str, value: str) -> Generator[None, None, None]:
+    """Context manager to temporarily patch an environment variable."""
+    old_value = os.getenv(name)
+    os.environ[name] = value
+    try:
+        yield
+    finally:
+        if old_value is None:
+            del os.environ[name]
+        else:
+            os.environ[name] = old_value
+
+
 def rmtree(path: PathLike) -> None:
     """Remove the given recursively.
 
@@ -935,7 +949,7 @@ def _obtain_lock_or_raise(self) -> None:
             )
 
         try:
-            with open(lock_file, mode='w'):
+            with open(lock_file, mode="w"):
                 pass
         except OSError as e:
             raise IOError(str(e)) from e