diff --git a/git/index/util.py b/git/index/util.py
index 1c3b1c4ad..61039fe7c 100644
--- a/git/index/util.py
+++ b/git/index/util.py
@@ -41,7 +41,8 @@ class TemporaryFileSwap:
 
     def __init__(self, file_path: PathLike) -> None:
         self.file_path = file_path
-        fd, self.tmp_file_path = tempfile.mkstemp(prefix=self.file_path, dir="")
+        dirname, basename = osp.split(file_path)
+        fd, self.tmp_file_path = tempfile.mkstemp(prefix=basename, dir=dirname)
         os.close(fd)
         with contextlib.suppress(OSError):  # It may be that the source does not exist.
             os.replace(self.file_path, self.tmp_file_path)
diff --git a/test/test_blob_filter.py b/test/test_blob_filter.py
index a91f211bf..ddd83079a 100644
--- a/test/test_blob_filter.py
+++ b/test/test_blob_filter.py
@@ -14,14 +14,15 @@
 from git.types import PathLike
 
 
-# fmt: off
-@pytest.mark.parametrize('paths, path, expected_result', [
-    ((Path("foo"),), Path("foo"), True),
-    ((Path("foo"),), Path("foo/bar"), True),
-    ((Path("foo/bar"),), Path("foo"), False),
-    ((Path("foo"), Path("bar")), Path("foo"), True),
-])
-# fmt: on
+@pytest.mark.parametrize(
+    "paths, path, expected_result",
+    [
+        ((Path("foo"),), Path("foo"), True),
+        ((Path("foo"),), Path("foo/bar"), True),
+        ((Path("foo/bar"),), Path("foo"), False),
+        ((Path("foo"), Path("bar")), Path("foo"), True),
+    ],
+)
 def test_blob_filter(paths: Sequence[PathLike], path: PathLike, expected_result: bool) -> None:
     """Test the blob filter."""
     blob_filter = BlobFilter(paths)
diff --git a/test/test_index.py b/test/test_index.py
index 2f97f0af8..c3f3b4fae 100644
--- a/test/test_index.py
+++ b/test/test_index.py
@@ -34,10 +34,11 @@
 )
 from git.index.fun import hook_path
 from git.index.typ import BaseIndexEntry, IndexEntry
+from git.index.util import TemporaryFileSwap
 from git.objects import Blob
-from test.lib import TestBase, fixture, fixture_path, with_rw_directory, with_rw_repo
 from git.util import Actor, hex_to_bin, rmtree
 from gitdb.base import IStream
+from test.lib import TestBase, fixture, fixture_path, with_rw_directory, with_rw_repo
 
 HOOKS_SHEBANG = "#!/usr/bin/env sh\n"
 
@@ -1087,3 +1088,25 @@ def test_index_add_pathlike(self, rw_repo):
         file.touch()
 
         rw_repo.index.add(file)
+
+
+class TestIndexUtils:
+    @pytest.mark.parametrize("file_path_type", [str, Path])
+    def test_temporary_file_swap(self, tmp_path, file_path_type):
+        file_path = tmp_path / "foo"
+        file_path.write_bytes(b"some data")
+
+        with TemporaryFileSwap(file_path_type(file_path)) as ctx:
+            assert Path(ctx.file_path) == file_path
+            assert not file_path.exists()
+
+            # Recreate it with new data, so we can observe that they're really separate.
+            file_path.write_bytes(b"other data")
+
+            temp_file_path = Path(ctx.tmp_file_path)
+            assert temp_file_path.parent == file_path.parent
+            assert temp_file_path.name.startswith(file_path.name)
+            assert temp_file_path.read_bytes() == b"some data"
+
+        assert not temp_file_path.exists()
+        assert file_path.read_bytes() == b"some data"  # Not b"other data".