diff --git a/archive.c b/archive.c
index ca11db185b15..b10269aee7be 100644
--- a/archive.c
+++ b/archive.c
@@ -339,7 +339,8 @@ int write_archive_entries(struct archiver_args *args,
 		opts.src_index = args->repo->index;
 		opts.dst_index = args->repo->index;
 		opts.fn = oneway_merge;
-		init_tree_desc(&t, args->tree->buffer, args->tree->size);
+		init_tree_desc(&t, &args->tree->object.oid,
+			       args->tree->buffer, args->tree->size);
 		if (unpack_trees(1, &t, &opts))
 			return -1;
 		git_attr_set_direction(GIT_ATTR_INDEX);
diff --git a/builtin/am.c b/builtin/am.c
index 8bde034fae68..4dfd714b910e 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1991,8 +1991,8 @@ static int fast_forward_to(struct tree *head, struct tree *remote, int reset)
 	opts.reset = reset ? UNPACK_RESET_PROTECT_UNTRACKED : 0;
 	opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 	opts.fn = twoway_merge;
-	init_tree_desc(&t[0], head->buffer, head->size);
-	init_tree_desc(&t[1], remote->buffer, remote->size);
+	init_tree_desc(&t[0], &head->object.oid, head->buffer, head->size);
+	init_tree_desc(&t[1], &remote->object.oid, remote->buffer, remote->size);
 
 	if (unpack_trees(2, t, &opts)) {
 		rollback_lock_file(&lock_file);
@@ -2026,7 +2026,7 @@ static int merge_tree(struct tree *tree)
 	opts.dst_index = &the_index;
 	opts.merge = 1;
 	opts.fn = oneway_merge;
-	init_tree_desc(&t[0], tree->buffer, tree->size);
+	init_tree_desc(&t[0], &tree->object.oid, tree->buffer, tree->size);
 
 	if (unpack_trees(1, t, &opts)) {
 		rollback_lock_file(&lock_file);
diff --git a/builtin/checkout.c b/builtin/checkout.c
index f53612f46870..03eff73fd031 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -701,7 +701,7 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 			       info->commit ? &info->commit->object.oid : null_oid(),
 			       NULL);
 	parse_tree(tree);
-	init_tree_desc(&tree_desc, tree->buffer, tree->size);
+	init_tree_desc(&tree_desc, &tree->object.oid, tree->buffer, tree->size);
 	switch (unpack_trees(1, &tree_desc, &opts)) {
 	case -2:
 		*writeout_error = 1;
@@ -815,10 +815,12 @@ static int merge_working_tree(const struct checkout_opts *opts,
 			die(_("unable to parse commit %s"),
 				oid_to_hex(old_commit_oid));
 
-		init_tree_desc(&trees[0], tree->buffer, tree->size);
+		init_tree_desc(&trees[0], &tree->object.oid,
+			       tree->buffer, tree->size);
 		parse_tree(new_tree);
 		tree = new_tree;
-		init_tree_desc(&trees[1], tree->buffer, tree->size);
+		init_tree_desc(&trees[1], &tree->object.oid,
+			       tree->buffer, tree->size);
 
 		ret = unpack_trees(2, trees, &topts);
 		clear_unpack_trees_porcelain(&topts);
diff --git a/builtin/clone.c b/builtin/clone.c
index c6357af94989..79ceefb93995 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -737,7 +737,7 @@ static int checkout(int submodule_progress, int filter_submodules)
 	if (!tree)
 		die(_("unable to parse commit %s"), oid_to_hex(&oid));
 	parse_tree(tree);
-	init_tree_desc(&t, tree->buffer, tree->size);
+	init_tree_desc(&t, &tree->object.oid, tree->buffer, tree->size);
 	if (unpack_trees(1, &t, &opts) < 0)
 		die(_("unable to checkout working tree"));
 
diff --git a/builtin/commit.c b/builtin/commit.c
index 7da5f924484d..537319932b65 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -340,7 +340,7 @@ static void create_base_index(const struct commit *current_head)
 	if (!tree)
 		die(_("failed to unpack HEAD tree object"));
 	parse_tree(tree);
-	init_tree_desc(&t, tree->buffer, tree->size);
+	init_tree_desc(&t, &tree->object.oid, tree->buffer, tree->size);
 	if (unpack_trees(1, &t, &opts))
 		exit(128); /* We've already reported the error, finish dying */
 }
diff --git a/builtin/grep.c b/builtin/grep.c
index 50e712a18479..0c2b8a376f8e 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -530,7 +530,7 @@ static int grep_submodule(struct grep_opt *opt,
 		strbuf_addstr(&base, filename);
 		strbuf_addch(&base, '/');
 
-		init_tree_desc(&tree, data, size);
+		init_tree_desc(&tree, oid, data, size);
 		hit = grep_tree(&subopt, pathspec, &tree, &base, base.len,
 				object_type == OBJ_COMMIT);
 		strbuf_release(&base);
@@ -574,7 +574,7 @@ static int grep_cache(struct grep_opt *opt,
 
 			data = repo_read_object_file(the_repository, &ce->oid,
 						     &type, &size);
-			init_tree_desc(&tree, data, size);
+			init_tree_desc(&tree, &ce->oid, data, size);
 
 			hit |= grep_tree(opt, pathspec, &tree, &name, 0, 0);
 			strbuf_setlen(&name, name_base_len);
@@ -670,7 +670,7 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
 				    oid_to_hex(&entry.oid));
 
 			strbuf_addch(base, '/');
-			init_tree_desc(&sub, data, size);
+			init_tree_desc(&sub, &entry.oid, data, size);
 			hit |= grep_tree(opt, pathspec, &sub, base, tn_len,
 					 check_attr);
 			free(data);
@@ -714,7 +714,7 @@ static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
 			strbuf_add(&base, name, len);
 			strbuf_addch(&base, ':');
 		}
-		init_tree_desc(&tree, data, size);
+		init_tree_desc(&tree, &obj->oid, data, size);
 		hit = grep_tree(opt, pathspec, &tree, &base, base.len,
 				obj->type == OBJ_COMMIT);
 		strbuf_release(&base);
diff --git a/builtin/merge.c b/builtin/merge.c
index de68910177fb..718165d45917 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -704,7 +704,8 @@ static int read_tree_trivial(struct object_id *common, struct object_id *head,
 	cache_tree_free(&the_index.cache_tree);
 	for (i = 0; i < nr_trees; i++) {
 		parse_tree(trees[i]);
-		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
+		init_tree_desc(t+i, &trees[i]->object.oid,
+			       trees[i]->buffer, trees[i]->size);
 	}
 	if (unpack_trees(nr_trees, t, &opts))
 		return -1;
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index d2a162d52804..d34902002656 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1756,7 +1756,8 @@ static void add_pbase_object(struct tree_desc *tree,
 			tree = pbase_tree_get(&entry.oid);
 			if (!tree)
 				return;
-			init_tree_desc(&sub, tree->tree_data, tree->tree_size);
+			init_tree_desc(&sub, &tree->oid,
+				       tree->tree_data, tree->tree_size);
 
 			add_pbase_object(&sub, down, downlen, fullname);
 			pbase_tree_put(tree);
@@ -1816,7 +1817,8 @@ static void add_preferred_base_object(const char *name)
 		}
 		else {
 			struct tree_desc tree;
-			init_tree_desc(&tree, it->pcache.tree_data, it->pcache.tree_size);
+			init_tree_desc(&tree, &it->pcache.oid,
+				       it->pcache.tree_data, it->pcache.tree_size);
 			add_pbase_object(&tree, name, cmplen, name);
 		}
 	}
diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 1fec702a04fa..24d6d156d3a2 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -264,7 +264,7 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
 	for (i = 0; i < nr_trees; i++) {
 		struct tree *tree = trees[i];
 		parse_tree(tree);
-		init_tree_desc(t+i, tree->buffer, tree->size);
+		init_tree_desc(t+i, &tree->object.oid, tree->buffer, tree->size);
 	}
 	if (unpack_trees(nr_trees, t, &opts))
 		return 128;
diff --git a/builtin/stash.c b/builtin/stash.c
index fe64cde9ce30..9ee52af4d28e 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -285,7 +285,7 @@ static int reset_tree(struct object_id *i_tree, int update, int reset)
 	if (parse_tree(tree))
 		return -1;
 
-	init_tree_desc(t, tree->buffer, tree->size);
+	init_tree_desc(t, &tree->object.oid, tree->buffer, tree->size);
 
 	opts.head_idx = 1;
 	opts.src_index = &the_index;
@@ -871,7 +871,8 @@ static void diff_include_untracked(const struct stash_info *info, struct diff_op
 		tree[i] = parse_tree_indirect(oid[i]);
 		if (parse_tree(tree[i]) < 0)
 			die(_("failed to parse tree"));
-		init_tree_desc(&tree_desc[i], tree[i]->buffer, tree[i]->size);
+		init_tree_desc(&tree_desc[i], &tree[i]->object.oid,
+			       tree[i]->buffer, tree[i]->size);
 	}
 
 	unpack_tree_opt.head_idx = -1;
diff --git a/cache-tree.c b/cache-tree.c
index ddc7d3d86959..334973a01cee 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -770,7 +770,7 @@ static void prime_cache_tree_rec(struct repository *r,
 
 	oidcpy(&it->oid, &tree->object.oid);
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 	cnt = 0;
 	while (tree_entry(&desc, &entry)) {
 		if (!S_ISDIR(entry.mode))
diff --git a/delta-islands.c b/delta-islands.c
index 5de5759f3f13..1ff3506b10f2 100644
--- a/delta-islands.c
+++ b/delta-islands.c
@@ -289,7 +289,7 @@ void resolve_tree_islands(struct repository *r,
 		if (!tree || parse_tree(tree) < 0)
 			die(_("bad tree object %s"), oid_to_hex(&ent->idx.oid));
 
-		init_tree_desc(&desc, tree->buffer, tree->size);
+		init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 		while (tree_entry(&desc, &entry)) {
 			struct object *obj;
 
diff --git a/diff-lib.c b/diff-lib.c
index 6b0c6a7180cc..add323f5628d 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -558,7 +558,7 @@ static int diff_cache(struct rev_info *revs,
 	opts.pathspec = &revs->diffopt.pathspec;
 	opts.pathspec->recursive = 1;
 
-	init_tree_desc(&t, tree->buffer, tree->size);
+	init_tree_desc(&t, &tree->object.oid, tree->buffer, tree->size);
 	return unpack_trees(1, &t, &opts);
 }
 
diff --git a/fsck.c b/fsck.c
index 2b1e348005b7..6b492a48da82 100644
--- a/fsck.c
+++ b/fsck.c
@@ -313,7 +313,8 @@ static int fsck_walk_tree(struct tree *tree, void *data, struct fsck_options *op
 		return -1;
 
 	name = fsck_get_object_name(options, &tree->object.oid);
-	if (init_tree_desc_gently(&desc, tree->buffer, tree->size, 0))
+	if (init_tree_desc_gently(&desc, &tree->object.oid,
+				  tree->buffer, tree->size, 0))
 		return -1;
 	while (tree_entry_gently(&desc, &entry)) {
 		struct object *obj;
@@ -583,7 +584,8 @@ static int fsck_tree(const struct object_id *tree_oid,
 	const char *o_name;
 	struct name_stack df_dup_candidates = { NULL };
 
-	if (init_tree_desc_gently(&desc, buffer, size, TREE_DESC_RAW_MODES)) {
+	if (init_tree_desc_gently(&desc, tree_oid, buffer, size,
+				  TREE_DESC_RAW_MODES)) {
 		retval += report(options, tree_oid, OBJ_TREE,
 				 FSCK_MSG_BAD_TREE,
 				 "cannot be parsed as a tree");
diff --git a/http-push.c b/http-push.c
index a704f490fdb2..81c35b5e96f7 100644
--- a/http-push.c
+++ b/http-push.c
@@ -1308,7 +1308,7 @@ static struct object_list **process_tree(struct tree *tree,
 	obj->flags |= SEEN;
 	p = add_one_object(obj, p);
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 
 	while (tree_entry(&desc, &entry))
 		switch (object_type(entry.mode)) {
diff --git a/list-objects.c b/list-objects.c
index e60a6cd5b46e..312335c8a7f2 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -97,7 +97,7 @@ static void process_tree_contents(struct traversal_context *ctx,
 	enum interesting match = ctx->revs->diffopt.pathspec.nr == 0 ?
 		all_entries_interesting : entry_not_interesting;
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 
 	while (tree_entry(&desc, &entry)) {
 		if (match != all_entries_interesting) {
diff --git a/match-trees.c b/match-trees.c
index 0885ac681cd5..3412b6a1401d 100644
--- a/match-trees.c
+++ b/match-trees.c
@@ -63,7 +63,7 @@ static void *fill_tree_desc_strict(struct tree_desc *desc,
 		die("unable to read tree (%s)", oid_to_hex(hash));
 	if (type != OBJ_TREE)
 		die("%s is not a tree", oid_to_hex(hash));
-	init_tree_desc(desc, buffer, size);
+	init_tree_desc(desc, hash, buffer, size);
 	return buffer;
 }
 
@@ -194,7 +194,7 @@ static int splice_tree(const struct object_id *oid1, const char *prefix,
 	buf = repo_read_object_file(the_repository, oid1, &type, &sz);
 	if (!buf)
 		die("cannot read tree %s", oid_to_hex(oid1));
-	init_tree_desc(&desc, buf, sz);
+	init_tree_desc(&desc, oid1, buf, sz);
 
 	rewrite_here = NULL;
 	while (desc.size) {
diff --git a/merge-ort.c b/merge-ort.c
index 8631c997002d..3a5729c91e48 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -1679,9 +1679,10 @@ static int collect_merge_info(struct merge_options *opt,
 	parse_tree(merge_base);
 	parse_tree(side1);
 	parse_tree(side2);
-	init_tree_desc(t + 0, merge_base->buffer, merge_base->size);
-	init_tree_desc(t + 1, side1->buffer, side1->size);
-	init_tree_desc(t + 2, side2->buffer, side2->size);
+	init_tree_desc(t + 0, &merge_base->object.oid,
+		       merge_base->buffer, merge_base->size);
+	init_tree_desc(t + 1, &side1->object.oid, side1->buffer, side1->size);
+	init_tree_desc(t + 2, &side2->object.oid, side2->buffer, side2->size);
 
 	trace2_region_enter("merge", "traverse_trees", opt->repo);
 	ret = traverse_trees(NULL, 3, t, &info);
@@ -4400,9 +4401,9 @@ static int checkout(struct merge_options *opt,
 	unpack_opts.fn = twoway_merge;
 	unpack_opts.preserve_ignored = 0; /* FIXME: !opts->overwrite_ignore */
 	parse_tree(prev);
-	init_tree_desc(&trees[0], prev->buffer, prev->size);
+	init_tree_desc(&trees[0], &prev->object.oid, prev->buffer, prev->size);
 	parse_tree(next);
-	init_tree_desc(&trees[1], next->buffer, next->size);
+	init_tree_desc(&trees[1], &next->object.oid, next->buffer, next->size);
 
 	ret = unpack_trees(2, trees, &unpack_opts);
 	clear_unpack_trees_porcelain(&unpack_opts);
diff --git a/merge-recursive.c b/merge-recursive.c
index 6a4081bb0f52..93df9eecdd95 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -411,7 +411,7 @@ static inline int merge_detect_rename(struct merge_options *opt)
 static void init_tree_desc_from_tree(struct tree_desc *desc, struct tree *tree)
 {
 	parse_tree(tree);
-	init_tree_desc(desc, tree->buffer, tree->size);
+	init_tree_desc(desc, &tree->object.oid, tree->buffer, tree->size);
 }
 
 static int unpack_trees_start(struct merge_options *opt,
diff --git a/merge.c b/merge.c
index b60925459c29..86179c34102d 100644
--- a/merge.c
+++ b/merge.c
@@ -81,7 +81,8 @@ int checkout_fast_forward(struct repository *r,
 	}
 	for (i = 0; i < nr_trees; i++) {
 		parse_tree(trees[i]);
-		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
+		init_tree_desc(t+i, &trees[i]->object.oid,
+			       trees[i]->buffer, trees[i]->size);
 	}
 
 	memset(&opts, 0, sizeof(opts));
diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index f6757c3cbf20..9211e08f0127 100644
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -366,7 +366,7 @@ static int fill_bitmap_tree(struct bitmap *bitmap,
 	if (parse_tree(tree) < 0)
 		die("unable to load tree object %s",
 		    oid_to_hex(&tree->object.oid));
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 
 	while (tree_entry(&desc, &entry)) {
 		switch (object_type(entry.mode)) {
diff --git a/packfile.c b/packfile.c
index 9cc0a2e37a83..1fae0fcdd9e7 100644
--- a/packfile.c
+++ b/packfile.c
@@ -2250,7 +2250,8 @@ static int add_promisor_object(const struct object_id *oid,
 		struct tree *tree = (struct tree *)obj;
 		struct tree_desc desc;
 		struct name_entry entry;
-		if (init_tree_desc_gently(&desc, tree->buffer, tree->size, 0))
+		if (init_tree_desc_gently(&desc, &tree->object.oid,
+					  tree->buffer, tree->size, 0))
 			/*
 			 * Error messages are given when packs are
 			 * verified, so do not print any here.
diff --git a/reflog.c b/reflog.c
index 9ad50e7d93e4..c6992a19268f 100644
--- a/reflog.c
+++ b/reflog.c
@@ -40,7 +40,7 @@ static int tree_is_complete(const struct object_id *oid)
 		tree->buffer = data;
 		tree->size = size;
 	}
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 	complete = 1;
 	while (tree_entry(&desc, &entry)) {
 		if (!repo_has_object_file(the_repository, &entry.oid) ||
diff --git a/revision.c b/revision.c
index 2f4c53ea207b..a60dfc23a2a5 100644
--- a/revision.c
+++ b/revision.c
@@ -82,7 +82,7 @@ static void mark_tree_contents_uninteresting(struct repository *r,
 	if (parse_tree_gently(tree, 1) < 0)
 		return;
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 	while (tree_entry(&desc, &entry)) {
 		switch (object_type(entry.mode)) {
 		case OBJ_TREE:
@@ -189,7 +189,7 @@ static void add_children_by_path(struct repository *r,
 	if (parse_tree_gently(tree, 1) < 0)
 		return;
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 	while (tree_entry(&desc, &entry)) {
 		switch (object_type(entry.mode)) {
 		case OBJ_TREE:
diff --git a/tree-walk.c b/tree-walk.c
index 3af50a01c2c7..0b44ec7c75ff 100644
--- a/tree-walk.c
+++ b/tree-walk.c
@@ -15,7 +15,7 @@ static int decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned l
 	const char *path;
 	unsigned int len;
 	uint16_t mode;
-	const unsigned hashsz = the_hash_algo->rawsz;
+	const unsigned hashsz = desc->algo->rawsz;
 
 	if (size < hashsz + 3 || buf[size - (hashsz + 1)]) {
 		strbuf_addstr(err, _("too-short tree object"));
@@ -37,15 +37,19 @@ static int decode_tree_entry(struct tree_desc *desc, const char *buf, unsigned l
 	desc->entry.path = path;
 	desc->entry.mode = (desc->flags & TREE_DESC_RAW_MODES) ? mode : canon_mode(mode);
 	desc->entry.pathlen = len - 1;
-	oidread(&desc->entry.oid, (const unsigned char *)path + len);
+	oidread_algop(&desc->entry.oid, (const unsigned char *)path + len,
+		      desc->algo);
 
 	return 0;
 }
 
-static int init_tree_desc_internal(struct tree_desc *desc, const void *buffer,
-				   unsigned long size, struct strbuf *err,
+static int init_tree_desc_internal(struct tree_desc *desc,
+				   const struct object_id *oid,
+				   const void *buffer, unsigned long size,
+				   struct strbuf *err,
 				   enum tree_desc_flags flags)
 {
+	desc->algo = (oid && oid->algo) ? &hash_algos[oid->algo] : the_hash_algo;
 	desc->buffer = buffer;
 	desc->size = size;
 	desc->flags = flags;
@@ -54,19 +58,21 @@ static int init_tree_desc_internal(struct tree_desc *desc, const void *buffer,
 	return 0;
 }
 
-void init_tree_desc(struct tree_desc *desc, const void *buffer, unsigned long size)
+void init_tree_desc(struct tree_desc *desc, const struct object_id *tree_oid,
+		    const void *buffer, unsigned long size)
 {
 	struct strbuf err = STRBUF_INIT;
-	if (init_tree_desc_internal(desc, buffer, size, &err, 0))
+	if (init_tree_desc_internal(desc, tree_oid, buffer, size, &err, 0))
 		die("%s", err.buf);
 	strbuf_release(&err);
 }
 
-int init_tree_desc_gently(struct tree_desc *desc, const void *buffer, unsigned long size,
+int init_tree_desc_gently(struct tree_desc *desc, const struct object_id *oid,
+			  const void *buffer, unsigned long size,
 			  enum tree_desc_flags flags)
 {
 	struct strbuf err = STRBUF_INIT;
-	int result = init_tree_desc_internal(desc, buffer, size, &err, flags);
+	int result = init_tree_desc_internal(desc, oid, buffer, size, &err, flags);
 	if (result)
 		error("%s", err.buf);
 	strbuf_release(&err);
@@ -85,7 +91,7 @@ void *fill_tree_descriptor(struct repository *r,
 		if (!buf)
 			die("unable to read tree %s", oid_to_hex(oid));
 	}
-	init_tree_desc(desc, buf, size);
+	init_tree_desc(desc, oid, buf, size);
 	return buf;
 }
 
@@ -102,7 +108,7 @@ static void entry_extract(struct tree_desc *t, struct name_entry *a)
 static int update_tree_entry_internal(struct tree_desc *desc, struct strbuf *err)
 {
 	const void *buf = desc->buffer;
-	const unsigned char *end = (const unsigned char *)desc->entry.path + desc->entry.pathlen + 1 + the_hash_algo->rawsz;
+	const unsigned char *end = (const unsigned char *)desc->entry.path + desc->entry.pathlen + 1 + desc->algo->rawsz;
 	unsigned long size = desc->size;
 	unsigned long len = end - (const unsigned char *)buf;
 
@@ -611,7 +617,7 @@ int get_tree_entry(struct repository *r,
 		retval = -1;
 	} else {
 		struct tree_desc t;
-		init_tree_desc(&t, tree, size);
+		init_tree_desc(&t, tree_oid, tree, size);
 		retval = find_tree_entry(r, &t, name, oid, mode);
 	}
 	free(tree);
@@ -654,7 +660,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 	struct tree_desc t;
 	int follows_remaining = GET_TREE_ENTRY_FOLLOW_SYMLINKS_MAX_LINKS;
 
-	init_tree_desc(&t, NULL, 0UL);
+	init_tree_desc(&t, NULL, NULL, 0UL);
 	strbuf_addstr(&namebuf, name);
 	oidcpy(&current_tree_oid, tree_oid);
 
@@ -690,7 +696,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 				goto done;
 
 			/* descend */
-			init_tree_desc(&t, tree, size);
+			init_tree_desc(&t, &current_tree_oid, tree, size);
 		}
 
 		/* Handle symlinks to e.g. a//b by removing leading slashes */
@@ -724,7 +730,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 			free(parent->tree);
 			parents_nr--;
 			parent = &parents[parents_nr - 1];
-			init_tree_desc(&t, parent->tree, parent->size);
+			init_tree_desc(&t, &parent->oid, parent->tree, parent->size);
 			strbuf_remove(&namebuf, 0, remainder ? 3 : 2);
 			continue;
 		}
@@ -804,7 +810,7 @@ enum get_oid_result get_tree_entry_follow_symlinks(struct repository *r,
 			contents_start = contents;
 
 			parent = &parents[parents_nr - 1];
-			init_tree_desc(&t, parent->tree, parent->size);
+			init_tree_desc(&t, &parent->oid, parent->tree, parent->size);
 			strbuf_splice(&namebuf, 0, len,
 				      contents_start, link_len);
 			if (remainder)
diff --git a/tree-walk.h b/tree-walk.h
index 74cdceb3fed2..cf54d01019e9 100644
--- a/tree-walk.h
+++ b/tree-walk.h
@@ -26,6 +26,7 @@ struct name_entry {
  * A semi-opaque data structure used to maintain the current state of the walk.
  */
 struct tree_desc {
+	const struct git_hash_algo *algo;
 	/*
 	 * pointer into the memory representation of the tree. It always
 	 * points at the current entry being visited.
@@ -85,9 +86,11 @@ int update_tree_entry_gently(struct tree_desc *);
  * size parameters are assumed to be the same as the buffer and size
  * members of `struct tree`.
  */
-void init_tree_desc(struct tree_desc *desc, const void *buf, unsigned long size);
+void init_tree_desc(struct tree_desc *desc, const struct object_id *tree_oid,
+		    const void *buf, unsigned long size);
 
-int init_tree_desc_gently(struct tree_desc *desc, const void *buf, unsigned long size,
+int init_tree_desc_gently(struct tree_desc *desc, const struct object_id *oid,
+			  const void *buf, unsigned long size,
 			  enum tree_desc_flags flags);
 
 /*
diff --git a/tree.c b/tree.c
index c745462f968e..44bcf728f10a 100644
--- a/tree.c
+++ b/tree.c
@@ -27,7 +27,7 @@ int read_tree_at(struct repository *r,
 	if (parse_tree(tree))
 		return -1;
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 
 	while (tree_entry(&desc, &entry)) {
 		if (retval != all_entries_interesting) {
diff --git a/walker.c b/walker.c
index 65002a7220ad..c0fd632d921c 100644
--- a/walker.c
+++ b/walker.c
@@ -45,7 +45,7 @@ static int process_tree(struct walker *walker, struct tree *tree)
 	if (parse_tree(tree))
 		return -1;
 
-	init_tree_desc(&desc, tree->buffer, tree->size);
+	init_tree_desc(&desc, &tree->object.oid, tree->buffer, tree->size);
 	while (tree_entry(&desc, &entry)) {
 		struct object *obj = NULL;
 
