_blank opening twice

Hi,

Hoping someone could help me. I have an amazon link and a custom field. For some reason the a href is opening in the current window and in a _blank window. Here is my code if someone could have a look…

<?php $amazon_aff_link_top_post = get_field('amazon_aff_link_top_post'); if ( $amazon_aff_link_top_post != false ) { ?>
<div class="post-top-button"><p style="margin:0;float:left;">Buy</p><a href="https://www.amazon.com/gp/search?ie=UTF8&tag=amazonID-20&keywords=<?php echo $amazon_aff_link_top_post; ?>" target="_blank" rel="nofollow"><img src="<?php bloginfo('template_directory'); ?>/images/buttons/amazon_buy_watching_sm.png" alt="buy on amazon" width="16" height="16" align="right" style="margin-top:1px;margin-left:8px;"></a></div>
 <?php } ?>

Cheers