diff --git a/git/index/base.py b/git/index/base.py
index 5ba817ed3..9d1db4e35 100644
--- a/git/index/base.py
+++ b/git/index/base.py
@@ -381,23 +381,21 @@ def from_tree(cls, repo: "Repo", *treeish: Treeish, **kwargs: Any) -> "IndexFile
             arg_list.append("--aggressive")
         # END merge handling
 
-        # tmp file created in git home directory to be sure renaming
-        # works - /tmp/ dirs could be on another device.
-        with contextlib.ExitStack() as stack:
-            tmp_index = stack.enter_context(_named_temporary_file_for_subprocess(repo.git_dir))
+        # Create the temporary file in the .git directory to be sure renaming
+        # works - /tmp/ directories could be on another device.
+        with _named_temporary_file_for_subprocess(repo.git_dir) as tmp_index:
             arg_list.append("--index-output=%s" % tmp_index)
             arg_list.extend(treeish)
 
-            # Move current index out of the way - otherwise the merge may fail
+            # Move the 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 ensures the original file gets 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)
-            index.entries  # Force it to read the file as we will delete the temp-file.
-            return index
+            with 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
             # END index merge handling
 
     # UTILITIES
diff --git a/git/index/util.py b/git/index/util.py
index 61039fe7c..125925783 100644
--- a/git/index/util.py
+++ b/git/index/util.py
@@ -15,7 +15,7 @@
 
 from typing import Any, Callable, TYPE_CHECKING, Optional, Type
 
-from git.types import PathLike, _T
+from git.types import Literal, PathLike, _T
 
 if TYPE_CHECKING:
     from git.index import IndexFile
@@ -55,7 +55,7 @@ def __exit__(
         exc_type: Optional[Type[BaseException]],
         exc_val: Optional[BaseException],
         exc_tb: Optional[TracebackType],
-    ) -> bool:
+    ) -> Literal[False]:
         if osp.isfile(self.tmp_file_path):
             os.replace(self.tmp_file_path, self.file_path)
         return False