Multiple select in new widgets api

Hey,

I seem to have a problem getting multiple selects to work on that widget I’m working on. Basically I have something like this:

<select class="widefat" id="<?php echo $this->get_field_id('thumbs'); ?>" multiple="multiple" size="7" style="height:100px" name="<?php echo $this->get_field_name('thumbs'); ?>[]">

Normally, the [] at the end in the name field means that it’s gonna be an array into which all of the selected options should be saved. But it doesn’t work and only saves the last option clicked.

Any ideas anybody?
Cheers!