How to make jekyll navbar show active on multiple pages

[Thingyman]

I'm making a website using jekyll, and I have a navbar set up and one of my pages is a blog. When I am on the blog, the navbar is normal and shows that you are on the blog. But on any of the posts, instead of showing you are in the blog, it shows that you are nowhere on the navbar. How can I fix this?

 

My blog.html

---
layout: default
title: Blog
description: Blog
---

<h1>Latest Posts</h1>

<ul>
  {% for post in site.posts %}
    <li>
      <h2><a href="{{ post.url }}">{{ post.title }}</a></h2>
      {{ post.excerpt }}
    </li>
  {% endfor %}
</ul>

 

My navbar

<div class="nav">
  <img src="/assets/images/Favicon.png" /><span><h1>Thingyman</h1></span>
  {% for item in site.data.navigation.items %}
  <a href="{{ site.baseurl }}{{ item.link }}" {% if page.url == item.url %}class="active" {% endif %}>
    {{ item.name }}
  </a>
{% endfor %}
</div>