Add one or more classes

Hi Ashley! I want to use my custom buttons so I pasted this in functions.php

function dedo_custom_button( $buttons ) {

	$custom_buttons =  array(
    'light-blue' => array(
        'name'      => __( 'Light Blue', 'delightful-downloads' ),
        'class'     => 'btn-light-blue'
    ),
    'orange'   	=> array(
        'name'      => __( 'Orange', 'delightful-downloads' ),
        'class'     => 'btn-orange'
    ),
    'white'    => array(
        'name'      => __( 'White', 'delightful-downloads' ),
        'class'     => 'btn-white'
    )
);

    return $custom_buttons;
}
add_filter( 'dedo_get_buttons', 'dedo_custom_button' );

I can see the 3 options from the dropdown of the shortcode generator and I think the generated code is correct [ddownload id=”159″ button=”light-blue”] but when I look at the html source the “btn-light-blue” class is missing.
It’s <a href="mysite.com/?ddownload=159" title="Download - 356,1 kB PDF" rel="nofollow" class="ddownload-link id-159 ext-pdf">Download - 356,1 kB PDF</a>

Also, I need to add a .btn class too class="ddownload-link id-159 ext-pdf btn btn-light-blue" Is it possible?

Thanks for this great plugin!