diff --git a/git/index/base.py b/git/index/base.py
index 1c56a219b..0f863b42c 100644
--- a/git/index/base.py
+++ b/git/index/base.py
@@ -351,7 +351,7 @@ def from_tree(cls, repo: "Repo", *treeish: Treeish, **kwargs: Any) -> "IndexFile
 
         # tmp file created in git home directory to be sure renaming
         # works - /tmp/ dirs could be on another device
-        tmp_index = tempfile.mktemp("", "", repo.git_dir)
+        tmp_index = tempfile.NamedTemporaryFile(dir=repo.git_dir, delete=True).name
         arg_list.append("--index-output=%s" % tmp_index)
         arg_list.extend(treeish)
 
diff --git a/git/index/util.py b/git/index/util.py
index bfc7fadd6..b837706de 100644
--- a/git/index/util.py
+++ b/git/index/util.py
@@ -40,7 +40,8 @@ class TemporaryFileSwap(object):
 
     def __init__(self, file_path: PathLike) -> None:
         self.file_path = file_path
-        self.tmp_file_path = str(self.file_path) + tempfile.mktemp("", "", "")
+        self.tmp_file_path = str(self.file_path) + osp.basename(tempfile.mkstemp("", "", "")[1])
+
         # it may be that the source does not exist
         try:
             os.rename(self.file_path, self.tmp_file_path)