diff --git a/core/modules/block/block.install b/core/modules/block/block.install
index 4771eee..3bf0cce 100644
--- a/core/modules/block/block.install
+++ b/core/modules/block/block.install
@@ -4,7 +4,6 @@
  * @file
  * Install, update, and uninstall functions for the Block module.
  */
-use Drupal\Core\Cache\Cache;
 
 /**
  * @addtogroup updates-8.0.0-beta
@@ -15,7 +14,7 @@
  * Update block visibility context mapping.
  */
 function block_update_8001() {
-  // This update function updates blocks for the change of
+  // This update function updates blocks for the change from
   // https://www.drupal.org/node/2354889
   //
   // Core visibility context plugins are updated automatically; blocks with
@@ -43,10 +42,8 @@ function block_update_8001() {
   // be executed before block_update_8002().
   /** @var \Drupal\Core\Config\StorageInterface $config_storage */
   $config_storage = \Drupal::service('config.storage');
-  $message = NULL;
-  $backup_values = [];
+  $backup_values = $update_backup = [];
 
-  $update_backup = [];
   foreach ($config_storage->listAll('block.block.') as $block_config_name) {
     $block = $config_storage->read($block_config_name);
     if ($visibility = $block['visibility']) {
@@ -55,7 +52,7 @@ function block_update_8001() {
           if (!isset($context_service_id_map[$key])) {
             // Remove the visibility condition for unknown context mapping
             // entries, so the update process itself runs through and users can
-            // fix their block placements manually OR alternatively contrib
+            // fix their block placements manually OR alternatively contributed
             // modules can run their own update functions to update mappings
             // that they provide.
             $backup_values[] = $context;
@@ -71,8 +68,9 @@ function block_update_8001() {
       $block['visibility'] = $visibility;
 
       if ($backup_values) {
-        // We not only store the missing context mappings but also the
-        // previous block status so contributed and custom modules could update.
+        // We not only store the missing context mappings but also the previous
+        // block status, in order to allow contributed and custom modules to do
+        // their own updates.
         $update_backup[$block['id']] = ['missing_context_ids' => $backup_values, 'status' => $block['id']];
       }
     }
@@ -83,15 +81,13 @@ function block_update_8001() {
   if ($update_backup) {
     \Drupal::keyValue('update_backup')->set('block_update_8001', $update_backup);
   }
-
-  return $message;
 }
 
 /**
- * Disables all blocks from the previous update.
+ * Disable all blocks from the previous update.
  */
 function block_update_8002() {
-  // Note: For this update function it's fine to use the entity API; see the
+  // Note: For this update function it's fine to use the Entity API; see the
   // explanation in block_update_8001().
   $block_update_8001 = \Drupal::keyValue('update_backup')->get('block_update_8001', []);
 
diff --git a/core/modules/block/tests/modules/block_test/src/Plugin/Condition/BaloneySpam.php b/core/modules/block/tests/modules/block_test/src/Plugin/Condition/BaloneySpam.php
index 06ecc8a..55e12ab 100644
--- a/core/modules/block/tests/modules/block_test/src/Plugin/Condition/BaloneySpam.php
+++ b/core/modules/block/tests/modules/block_test/src/Plugin/Condition/BaloneySpam.php
@@ -10,7 +10,7 @@
 use Drupal\Core\Condition\ConditionPluginBase;
 
 /**
- * Provides a 'baloney spam' condition.
+ * Provides a 'baloney.spam' condition.
  *
  * @Condition(
  *   id = "baloney.spam",
diff --git a/core/modules/system/tests/fixtures/update/drupal-8.block-context-manager-2354889.php b/core/modules/system/tests/fixtures/update/drupal-8.block-context-manager-2354889.php
index d3af4a1..23b67e5 100644
--- a/core/modules/system/tests/fixtures/update/drupal-8.block-context-manager-2354889.php
+++ b/core/modules/system/tests/fixtures/update/drupal-8.block-context-manager-2354889.php
@@ -10,10 +10,14 @@
 
 $connection = Database::getConnection();
 
-// Structure of a custom block with visibility settings.
-
+// A custom block with visibility settings.
 $block_configs[] = \Drupal\Component\Serialization\Yaml::decode(file_get_contents(__DIR__ . '/block.block.testfor2354889.yml'));
+
+// A custom block without any visibility settings.
 $block_configs[] = \Drupal\Component\Serialization\Yaml::decode(file_get_contents(__DIR__ . '/block.block.secondtestfor2354889.yml'));
+
+// A custom block with visibility settings that contain a non-existing context
+// mapping.
 $block_configs[] = \Drupal\Component\Serialization\Yaml::decode(file_get_contents(__DIR__ . '/block.block.thirdtestfor2354889.yml'));
 
 foreach ($block_configs as $block_config) {