aside.html

<div>
	<ul>
	{% for item in site.data.navigation.navsecondary %}

		<li>{{ item.title }}</li>

		{% if item.subnav %}

			<!-- This appears fine -->

			{% for subitem in site.data.navigation.navsecondary.subnav %}
                                {{ subnav.title }}
				<!-- Nothing coming out here though -->

			{% endfor %}

		{% endif %}

	{% endfor %}
	</ul>
</div>

navigation.yml

navprimary:
- title: Home
  url: /
- title: Blog
  url: /blog/

navsecondary:
- title: Getting Started
  url: /getting-started/
- title: Templating
  url: /templating/
  subnav:
  - title: Twig
    url: /templating/twig/
  - title: Twig
    url: /templating/twig/
  - title: Twig
    url: /templating/twig/