diff --git a/builtin/repack.c b/builtin/repack.c
index 632c0c0a79..5830f796e0 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -190,7 +190,7 @@ static int write_oid(const struct object_id *oid, struct packed_git *pack,
 			die(_("could not start pack-objects to repack promisor objects"));
 	}
 
-	xwrite(cmd->in, oid_to_hex(oid), GIT_SHA1_HEXSZ);
+	xwrite(cmd->in, oid_to_hex(oid), the_hash_algo->hexsz);
 	xwrite(cmd->in, "\n", 1);
 	return 0;
 }