diff --git a/core/modules/responsive_image/templates/responsive-image.html.twig b/core/modules/responsive_image/templates/responsive-image.html.twig
index 7e6099c..9a89043 100644
--- a/core/modules/responsive_image/templates/responsive-image.html.twig
+++ b/core/modules/responsive_image/templates/responsive-image.html.twig
@@ -25,5 +25,6 @@
     {% endfor %}
     <!--[if IE 9]></video><![endif]-->
   {% endif %}
+  {# The controlling image, with the fallback image in srcset. #}
   {{ img_element }}
 </picture>