exclude custom taxonomy

exclude_taxonomy.php

       <?php
        $args = array(
              'post_type'=>'casas',
              'posts_per_page'=>4,
              'orderby'=>'date',
              'order'=>'DESC',
              'tax_query' => array(
                array(
                    'taxonomy'=>'categorias_casas',
                    'field'     => 'slug',
                    'terms'     => array( 'agenda' ),
                    'operator'  => 'NOT IN',
                      ),
            )

        );
        $query = new WP_Query( $args);

        ?>
    <?php if ( $query->have_posts() ) : while ( $query->have_posts() ) : $query->the_post(); ?>