Which improvement would you recommend for the following Cloud Datastore code that adds a credit to an account balance?

public Entity creditAccount(long accountId, long creditAmount) {
    Entity account = datastore.get(keyFactory.newKey(accountId));
    account = Entity.builder(account)
                   .set("balance", account.getLong("balance") + creditAmount)
                   .build();
    datastore.put(account);
    return account;
}