diff --git a/core/themes/seven/css/base/elements.css b/core/themes/seven/css/base/elements.css
index 59795d3..7ba0d02 100644
--- a/core/themes/seven/css/base/elements.css
+++ b/core/themes/seven/css/base/elements.css
@@ -36,6 +36,13 @@ h3,
 h4,
 h5,
 h6,
+/**
+ * Classes '.heading-a' - '.heading-f' are not currently in use; they are still
+ * included in stylesheet to keep Seven and Bartik consistent and good examples
+ * of easy to configure base styles.
+ *
+ * @see https://www.drupal.org/node/2400233
+ */
 .heading-a,
 .heading-b,
 .heading-c,