diff --git a/apps/downloads/templates/downloads/supernav.html b/apps/downloads/templates/downloads/supernav.html
index edd23dc82..463cb35b8 100644
--- a/apps/downloads/templates/downloads/supernav.html
+++ b/apps/downloads/templates/downloads/supernav.html
@@ -1,7 +1,7 @@
 <!-- Download supernav from templates/downloads/supernav.html - Last updated at {{ last_updated }} -->
 <li class="tier-2 super-navigation">
     {% for data in python_files %}
-    <div class="download-os-{{ data.os.slug }}" style="display: none;">
+    <div class="download-os-{{ data.os.slug }}">
         {% if data.os.slug == 'source' %}
         <h3>Python Source</h3>
         {% else %}
diff --git a/static/css/mq.css b/static/css/mq.css
index 91134a5e7..a2cb44e7c 100644
--- a/static/css/mq.css
+++ b/static/css/mq.css
@@ -814,6 +814,10 @@ html[xmlns] .slides { display: block; }
   .with-supernav .super-navigation {
     display: none; }
 
+  /* Box sanitization strips inline styles; OS detection reveals the matching panel. */
+  .super-navigation [class^="download-os-"] {
+    display: none; }
+
   /*
    * This is super cool. Uses two arrays to spit out a bunch of repetitive rulesets.
    * Associative array example borrowed from https://github.com/nex3/sass/issues/132#issuecomment-4335097