"Open link in a new window/tab" not working

The open in a new window/tab option does not seem to work for me within a WordPress Menu.

If I toggle the option it does not append “target=”_blank”” to the anchor tag

<?php $leftNav = array(
	'theme_location' => 'left-menu-header',
	'container' => false,
	'echo' => true,
	'fallback_cb' => 'wp_page_menu',
	'before' => '',
	'after' => '',
	'link_before' => '',
	'link_after' => '',
	'items_wrap' => '%3$s',
	'walker' => new navWalker
	);
wp_nav_menu($leftNav); ?>

Which outputs

<ul class="header-nav hide-for-small-only">
	<li class="menu-item menu-item-type-post_type menu-item-object-page post-id-6"><a href="#">About</a></li>
	<li class="menu-item menu-item-type-post_type menu-item-object-page post-id-8"><a href="#">Press</a></li>
	<li class="menu-item menu-item-type-custom menu-item-object-custom post-id-15"><a href="https://#">Shop</a></li>
</ul>

Thanks in advanced…