diff --git a/archive-tar.c b/archive-tar.c
index 4aabd566fb..3e53aac1e6 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -326,14 +326,15 @@ static int write_tar_entry(struct archiver_args *args,
 
 static void write_global_extended_header(struct archiver_args *args)
 {
-	const unsigned char *sha1 = args->commit_sha1;
+	const struct object_id *oid = args->commit_oid;
 	struct strbuf ext_header = STRBUF_INIT;
 	struct ustar_header header;
 	unsigned int mode;
 
-	if (sha1)
+	if (oid)
 		strbuf_append_ext_header(&ext_header, "comment",
-					 sha1_to_hex(sha1), 40);
+					 oid_to_hex(oid),
+					 the_hash_algo->hexsz);
 	if (args->time > USTAR_MAX_MTIME) {
 		strbuf_append_ext_header_uint(&ext_header, "mtime",
 					      args->time);
diff --git a/archive-zip.c b/archive-zip.c
index 155ee4a779..4d66b5be6e 100644
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -577,7 +577,7 @@ static void write_zip64_trailer(void)
 	write_or_die(1, &locator64, ZIP64_DIR_TRAILER_LOCATOR_SIZE);
 }
 
-static void write_zip_trailer(const unsigned char *sha1)
+static void write_zip_trailer(const struct object_id *oid)
 {
 	struct zip_dir_trailer trailer;
 	int clamped = 0;
@@ -590,14 +590,14 @@ static void write_zip_trailer(const unsigned char *sha1)
 	copy_le16_clamp(trailer.entries, zip_dir_entries, &clamped);
 	copy_le32(trailer.size, zip_dir.len);
 	copy_le32_clamp(trailer.offset, zip_offset, &clamped);
-	copy_le16(trailer.comment_length, sha1 ? GIT_SHA1_HEXSZ : 0);
+	copy_le16(trailer.comment_length, oid ? the_hash_algo->hexsz : 0);
 
 	write_or_die(1, zip_dir.buf, zip_dir.len);
 	if (clamped)
 		write_zip64_trailer();
 	write_or_die(1, &trailer, ZIP_DIR_TRAILER_SIZE);
-	if (sha1)
-		write_or_die(1, sha1_to_hex(sha1), GIT_SHA1_HEXSZ);
+	if (oid)
+		write_or_die(1, oid_to_hex(oid), the_hash_algo->hexsz);
 }
 
 static void dos_time(timestamp_t *timestamp, int *dos_date, int *dos_time)
@@ -635,7 +635,7 @@ static int write_zip_archive(const struct archiver *ar,
 
 	err = write_archive_entries(args, write_zip_entry);
 	if (!err)
-		write_zip_trailer(args->commit_sha1);
+		write_zip_trailer(args->commit_oid);
 
 	strbuf_release(&zip_dir);
 
diff --git a/archive.c b/archive.c
index 1f98324a93..f2c78a2712 100644
--- a/archive.c
+++ b/archive.c
@@ -380,7 +380,7 @@ static void parse_treeish_arg(const char **argv,
 		int remote)
 {
 	const char *name = argv[0];
-	const unsigned char *commit_sha1;
+	const struct object_id *commit_oid;
 	time_t archive_time;
 	struct tree *tree;
 	const struct commit *commit;
@@ -402,10 +402,10 @@ static void parse_treeish_arg(const char **argv,
 
 	commit = lookup_commit_reference_gently(ar_args->repo, &oid, 1);
 	if (commit) {
-		commit_sha1 = commit->object.oid.hash;
+		commit_oid = &commit->object.oid;
 		archive_time = commit->date;
 	} else {
-		commit_sha1 = NULL;
+		commit_oid = NULL;
 		archive_time = time(NULL);
 	}
 
@@ -426,7 +426,7 @@ static void parse_treeish_arg(const char **argv,
 		tree = parse_tree_indirect(&tree_oid);
 	}
 	ar_args->tree = tree;
-	ar_args->commit_sha1 = commit_sha1;
+	ar_args->commit_oid = commit_oid;
 	ar_args->commit = commit;
 	ar_args->time = archive_time;
 }
diff --git a/archive.h b/archive.h
index 21ac010699..dd022a6b46 100644
--- a/archive.h
+++ b/archive.h
@@ -11,7 +11,7 @@ struct archiver_args {
 	const char *base;
 	size_t baselen;
 	struct tree *tree;
-	const unsigned char *commit_sha1;
+	const struct object_id *commit_oid;
 	const struct commit *commit;
 	timestamp_t time;
 	struct pathspec pathspec;