How to display unlimited post in Taxonomy pages

Hi guys,

How do you display unlimited post in taxonomy page (ex: taxonomy-gallery_categories.php) this came from CPT gallery, and its not working. In default it only displays 10 posts.. anyone would like to help me?

here’s my code: (from my taxonomy-gallery_categories.php file)

$wp_query = new WP_Query( 'post_type=gallery&posts_per_page=-1&cat=12' );
while ($wp_query->have_posts()) : $wp_query->the_post();
//contents here...
endwhile;

thank you very much!