diff --git a/core/modules/block/js/block.admin.js b/core/modules/block/js/block.admin.js
index 9f99b7f..850aa63 100644
--- a/core/modules/block/js/block.admin.js
+++ b/core/modules/block/js/block.admin.js
@@ -56,6 +56,12 @@
         // Filter if the length of the query is at least 2 characters.
         if (query.length >= 2) {
           $filter_rows.each(toggleBlockEntry);
+          Drupal.announce(
+              Drupal.formatPlural(
+                  '!blocks blocks are available in the modified list.',
+                  {'!blocks': $('table.block-add-table tr:visible').length - 1}
+              )
+          );
         }
         else {
           $filter_rows.each(function (index) {