def get_initial_lock_expiration(block_number, settle_timeout):
    """ Returns the expiration for first hash-time-lock in a mediated transfer. """
    # The initiator doesn't need to learn the secret, so there is no need to
    # decrement reveal_timeout from the settle_timeout.
    #
    # The lock_expiration could be set to a value larger than settle_timeout,
    # this is not useful since the next hop will use the channel settle_timeout
    # as an upper limit for expiration.
    #
    # The two nodes will most likely disagree on the latest block number, as
    # far as the expiration goes this is no problem.
    lock_expiration = block_number + settle_timeout
    return lock_expiration