diff --git a/core/modules/block/lib/Drupal/block/BlockBase.php b/core/modules/block/lib/Drupal/block/BlockBase.php
index 9cb7355..a043db5 100644
--- a/core/modules/block/lib/Drupal/block/BlockBase.php
+++ b/core/modules/block/lib/Drupal/block/BlockBase.php
@@ -485,6 +485,8 @@ public function buildBlock() {
           'label' => check_plain($this->configuration['label']),
         ),
       );
+      // Label needs special handling.
+      $build['#block']->label = check_plain($this->configuration['label']);
       $build['content'] = $content;
     }