diff --git a/_includes/header.html b/_includes/header.html
index 927773b22..ea38eef2f 100644
--- a/_includes/header.html
+++ b/_includes/header.html
@@ -22,7 +22,7 @@ <h1 class="panel-cover__title panel-title">{{ site.title }}</h1>
             <ul class="navigation">
 
               <!-- https://mastodon.social/@tzuehlke@mstdn.social -->
-            {% if site.author.twitter_username %}
+            {% if site.author.mastodon %}
               <!-- Mastodon -->
               <li class="navigation__item">
                 <a href="https://mastodon.social/@{{ site.author.mastodon }}" title="@{{ site.author.mastodon }} on Mastodon" target="_blank">