I believe you have to "register" the account again, but you won't pay the delegate fee just a transaction fee (could someone else confirm that he won't pay delegate fee?) see below:
>> help wallet_account_register
Usage:
wallet_account_register <account_name> <pay_from_account> [public_data] [delegate_pay_rate] Updates the data published about a given account
Updates the data published about a given account
Parameters:
account_name (account_name, required): the account that will be updated
pay_from_account (account_name, required): the account from which fees will be paid
public_data (json_variant, optional, defaults to null): public data about the account
delegate_pay_rate (uint32_t, optional, defaults to 255): A value between 0 and 100 for delegates, 255 for non delegates
Returns:
signed_transaction
aliases: register