How can I make "Select category" first option in category select dropdown?

How can I make the “Select category” option the first in the drop down list? It will only put “Show all posts” as the first option. this is my code:

<?php $args = array('show_option_none' => 'Select category',
'show_option_all' => 'Show all posts'); ?>
<?php wp_dropdown_categories( $args ); ?>

and this is the outputted html:

<select name='cat' id='cat' class='postform' >
	<option value='0'>Show all posts</option>
	<option value='-1'>Select category</option>
	<option class="level-0" value="1">Uncategorized</option>
	<option class="level-0" value="8">Blog</option>
</select>

you’d think that a simple 'orderby' => 'ID' or 'orderby' => 'value' would do it, but it doesnt.. i don’t want to just make the “select category” the selected option by default because then when you’re on a specific category page it will still be selected. i just want to change the output to this:

<select name='cat' id='cat' class='postform' >
	<option value='-1'>Select category</option>
	<option value='0'>Show all posts</option>
	<option class="level-0" value="1">Uncategorized</option>
	<option class="level-0" value="8">Blog</option>
</select>