around('initialize_instance_slot', sub {
    my $orig = shift;
    my $self = shift;

    my $ia = $self->init_arg;

    # $_[2] is the hashref of options passed to the constructor. If our
    # parameter passed in was undef, pop it off the args...
    pop unless (exists($_[2]->{$ia}) && defined($_[2]->{$ia}));

    # Invoke the real init, as the above line cleared the unef
    $self->$orig(@_)
});