Center Image layout in MarketPress

On line 1552 of marketpress-includes/template-functions.php it aligns the images to the left. I can change to right, but I want them centered. What do I need to change to center the images?

$image = get_the_post_thumbnail($post_id, $size, array('class' => 'alignleft mp_product_image_'.$context, 'title' => $title));

Thanks!