diff -u b/core/modules/system/templates/progress-bar.html.twig b/core/modules/system/templates/progress-bar.html.twig
--- b/core/modules/system/templates/progress-bar.html.twig
+++ b/core/modules/system/templates/progress-bar.html.twig
@@ -18,7 +18,7 @@
   {% if label %}
     <div class="progress__label">{{ label }}</div>
   {% endif %}
-  <div class="progress__track"><div class="progress__bar {% if static %}progress__bar--static{% endif %}" style="width: {{ percent }}%"></div></div>
+  <div class="progress__track"><div class="progress__bar{% if static %} progress__bar--static{% endif %}" style="width: {{ percent }}%"></div></div>
   <div class="progress__percentage">{{ percent }}%</div>
   <div class="progress__description">{{ message }}</div>
 </div>