diff --git a/git/index/base.py b/git/index/base.py
index 8523717c6..dd8f9aa2e 100644
--- a/git/index/base.py
+++ b/git/index/base.py
@@ -353,26 +353,22 @@ 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)
-        arg_list.append("--index-output=%s" % tmp_index)
-        arg_list.extend(treeish)
-
-        # move current index out of the way - otherwise the merge may fail
-        # as it considers existing entries. moving it essentially clears the index.
-        # Unfortunately there is no 'soft' way to do it.
-        # The TemporaryFileSwap assure the original file get put back
-        try:
-            with ExitStack() as stack:
-                if repo.git_dir:
-                    stack.enter_context(TemporaryFileSwap(join_path_native(repo.git_dir, "index")))
-                repo.git.read_tree(*arg_list, **kwargs)
-                index = cls(repo, tmp_index)
-                index.entries  # force it to read the file as we will delete the temp-file
-                return index
-        finally:
-            if osp.exists(tmp_index):
-                os.remove(tmp_index)
-        # END index merge handling
+        with ExitStack() as stack:
+            tmp_index = stack.enter_context(tempfile.NamedTemporaryFile(dir=repo.git_dir))
+            arg_list.append("--index-output=%s" % tmp_index.name)
+            arg_list.extend(treeish)
+
+            # move current index out of the way - otherwise the merge may fail
+            # as it considers existing entries. moving it essentially clears the index.
+            # Unfortunately there is no 'soft' way to do it.
+            # The TemporaryFileSwap assure the original file get put back
+
+            stack.enter_context(TemporaryFileSwap(join_path_native(repo.git_dir, "index")))
+            repo.git.read_tree(*arg_list, **kwargs)
+            index = cls(repo, tmp_index.name)
+            index.entries  # force it to read the file as we will delete the temp-file
+            return index
+            # END index merge handling
 
     # UTILITIES
     @unbare_repo