diff --git a/core/includes/update.inc b/core/includes/update.inc
index f0020ee..67af504 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -219,26 +219,26 @@ function update_do_one($module, $number, $dependency_map, &$context) {
 }
 
 /**
- * Executes a single hook_update_after_$name().
+ * Executes a single hook_post_update_$name().
  *
  * @param string $function
  *   The function name, that should be executed.
  * @param array $context
  *   The batch context array.
  */
-function update_after_do_one($function, &$context) {
+function update_post_update_do_one($function, &$context) {
   $ret = [];
-  list($module, ) = explode('_update_after_', $function);
-  module_load_include('inc', $module, $module . '.update_after');
+  list($module, ) = explode('_post_update_', $function);
+  module_load_include('php', $module, $module . '.post_update');
   if (function_exists($function)) {
     try {
       $ret['results']['query'] = $function($context['sandbox']);
       $ret['results']['success'] = TRUE;
 
-      $key_value_store = \Drupal::keyValue('update_after');
-      $executed_updates = $key_value_store->get('core.update__update_after', []);
+      $key_value_store = \Drupal::keyValue('update_test_post_update');
+      $executed_updates = $key_value_store->get('core.update__post_update', []);
       $executed_updates[] = $function;
-      $key_value_store->set('core.update__update_after', $executed_updates);
+      $key_value_store->set('core.update__post_update', $executed_updates);
     }
       // @TODO We may want to do different error handling for different
       // exception types, but for now we'll just log the exception and
diff --git a/core/lib/Drupal/Core/Extension/module.api.php b/core/lib/Drupal/Core/Extension/module.api.php
index 6bc62d1..264dc4c 100644
--- a/core/lib/Drupal/Core/Extension/module.api.php
+++ b/core/lib/Drupal/Core/Extension/module.api.php
@@ -686,7 +686,7 @@ function hook_update_N(&$sandbox) {
  *
  * @see hook_update_N
  */
-function hook_update_after_X(&$sandbox) {
+function hook_post_update_X(&$sandbox) {
   $node = \Drupal\node\Entity\Node::load(123);
   $node->setTitle('foo');
   $node->save();
diff --git a/core/lib/Drupal/Core/Update/UpdateRegistry.php b/core/lib/Drupal/Core/Update/UpdateRegistry.php
index 58ec918..b7d3b67 100644
--- a/core/lib/Drupal/Core/Update/UpdateRegistry.php
+++ b/core/lib/Drupal/Core/Update/UpdateRegistry.php
@@ -12,14 +12,14 @@
 use Drupal\Core\KeyValueStore\KeyValueStoreInterface;
 
 /**
- * Provides all and missing hook_update_$updateName_X implementations.
+ * Provides all and missing hook_$updateName_X implementations.
  *
  * It therefore scans for functions in $module.$updateName.inc named like
- * $module_update_$updateName_X with X being a machine name.
+ * $module_$updateName_X with X being a machine name.
  */
 class UpdateRegistry {
 
-  protected $updateName = 'update_after';
+  protected $updateName = 'post_update';
 
   /**
    * The app root.
@@ -126,7 +126,7 @@ protected function loadUpdateFiles(array $module_extensions) {
    * @param \Drupal\Core\Extension\Extension $module
    */
   protected function loadUpdateFile(Extension $module) {
-    $filename = $this->root . '/' . $module->getPath() . '/' . $module->getName() . ".{$this->updateName}.inc";
+    $filename = $this->root . '/' . $module->getPath() . '/' . $module->getName() . ".{$this->updateName}.php";
     if (file_exists($filename)) {
       include_once $filename;
     }
@@ -158,7 +158,7 @@ public function getMissingUpdateList() {
       // The description for an update comes from its Doxygen.
       $func = new \ReflectionFunction($function);
       $description = trim(str_replace(array("\n", '*', '/'), '', $func->getDocComment()), ' ');
-      $ret[$module]['pending'][$update] = "$update - $description";
+      $ret[$module]['pending'][$update] = "<!-- function: $function -->$description";
       if (!isset($ret[$module]['start'])) {
         $ret[$module]['start'] = $update;
       }
diff --git a/core/modules/system/src/Controller/DbUpdateController.php b/core/modules/system/src/Controller/DbUpdateController.php
index d935d50..ab06793 100644
--- a/core/modules/system/src/Controller/DbUpdateController.php
+++ b/core/modules/system/src/Controller/DbUpdateController.php
@@ -259,12 +259,12 @@ protected function selection(Request $request) {
     $build['start']['system'] = array();
 
     $starting_updates = array();
-    foreach (['update', 'update_after'] as $update_type) {
+    foreach (['update', 'post_update'] as $update_type) {
       switch ($update_type) {
         case 'update':
           $updates = update_get_update_list();
           break;
-        case 'update_after':
+        case 'post_update':
           $after_update_registry = $this->getUpdateAfterRegistry();
           $updates = $after_update_registry->getMissingUpdateList();
           break;
@@ -590,14 +590,14 @@ protected function triggerBatch(Request $request) {
     }
 
     $after_update_registry = $this->getUpdateAfterRegistry();
-    $after_updates = $after_update_registry->getMissingUpdateFunctions();
+    $post_updates = $after_update_registry->getMissingUpdateFunctions();
 
-    if ($after_updates) {
-      // Now we rebuild all caches and after that execute the hook_update_after()
+    if ($post_updates) {
+      // Now we rebuild all caches and after that execute the hook_post_update()
       // functions.
       $operations[] = ['drupal_flush_all_caches', []];
-      foreach ($after_updates as $function) {
-        $operations[] = ['update_after_do_one', [$function]];
+      foreach ($post_updates as $function) {
+        $operations[] = ['update_post_update_do_one', [$function]];
       }
     }
 
@@ -616,12 +616,12 @@ protected function triggerBatch(Request $request) {
   }
 
   /**
-   * Gets the update registry instance for the hook_update_after updates.
+   * Gets the update registry instance for the hook_post_update updates.
    *
    * @return \Drupal\Core\Update\UpdateRegistry
    */
-  protected function getUpdateAfterRegistry() {
-    return new UpdateRegistry($this->root, \Drupal::service('site.path'), array_keys($this->moduleHandler()->getModuleList()), \Drupal::keyValue('update_after'));
+  protected function getPostUpdateRegistry() {
+    return new UpdateRegistry($this->root, \Drupal::service('site.path'), array_keys($this->moduleHandler()->getModuleList()), \Drupal::keyValue('post_update'));
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Update/UpdateAfterTest.php b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
similarity index 50%
rename from core/modules/system/src/Tests/Update/UpdateAfterTest.php
rename to core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
index 0b85fcb..e82b0c5 100644
--- a/core/modules/system/src/Tests/Update/UpdateAfterTest.php
+++ b/core/modules/system/src/Tests/Update/UpdatePostUpdateTest.php
@@ -2,17 +2,17 @@
 
 /**
  * @file
- * Contains \Drupal\system\Tests\Update\UpdateAfterTest.
+ * Contains \Drupal\system\Tests\Update\UpdatePostUpdateTest.
  */
 
 namespace Drupal\system\Tests\Update;
 
 /**
- * Tests hook_update_after().
+ * Tests hook_post_update().
  *
  * @group Update
  */
-class UpdateAfterTest extends UpdatePathTestBase {
+class UpdatePostUpdateTest extends UpdatePathTestBase {
 
   /**
    * {@inheritdoc}
@@ -20,7 +20,7 @@ class UpdateAfterTest extends UpdatePathTestBase {
   protected function setDatabaseDumpFiles() {
     $this->databaseDumpFiles = [
       __DIR__ . '/../../../tests/fixtures/update/drupal-8.bare.standard.php.gz',
-      __DIR__ . '/../../../tests/fixtures/update/drupal-8.update-test-after-enabled.php',
+      __DIR__ . '/../../../tests/fixtures/update/drupal-8.update-post-update-after-enabled.php',
     ];
   }
 
@@ -28,11 +28,11 @@ public function testUpdateAfter() {
     $this->runUpdates();
 
     $this->assertIdentical([
-      'update_test_after_update_after_first',
-      'update_test_after_update_after_second',
-      'update_test_after_update_after_test1',
-      'update_test_after_update_after_test0',
-    ], \Drupal::state()->get('update_test_after_execution', []));
+      'update_test_post_update_post_update_first',
+      'update_test_post_update_post_update_second',
+      'update_test_post_update_post_update_test1',
+      'update_test_post_update_post_update_test0',
+    ], \Drupal::state()->get('post_update_test_execution', []));
   }
 
 }
diff --git a/core/modules/system/tests/fixtures/update/drupal-8.update-test-after-enabled.php b/core/modules/system/tests/fixtures/update/drupal-8.update-test-post-update-enabled.php
similarity index 82%
rename from core/modules/system/tests/fixtures/update/drupal-8.update-test-after-enabled.php
rename to core/modules/system/tests/fixtures/update/drupal-8.update-test-post-update-enabled.php
index 681a5fb..3d5af10 100644
--- a/core/modules/system/tests/fixtures/update/drupal-8.update-test-after-enabled.php
+++ b/core/modules/system/tests/fixtures/update/drupal-8.update-test-post-update-enabled.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Partial database to mimic the installation of the update_test_after module.
+ * Partial database to mimic the installation of the update_test_post_update module.
  */
 
 use Drupal\Core\Database\Database;
@@ -12,10 +12,10 @@
 // Set the schema version.
 $connection->merge('key_value')
   ->condition('collection', 'system.schema')
-  ->condition('name', 'update_test_schema')
+  ->condition('name', 'update_test_post_update')
   ->fields([
     'collection' => 'system.schema',
-    'name' => 'update_test_after',
+    'name' => 'update_test_post_update',
     'value' => 'i:8000;',
   ])
   ->execute();
@@ -28,7 +28,7 @@
   ->execute()
   ->fetchField();
 $extensions = unserialize($extensions);
-$extensions['module']['update_test_after'] = 8000;
+$extensions['module']['update_test_post_update'] = 8000;
 $connection->update('config')
   ->fields([
     'data' => serialize($extensions),
diff --git a/core/modules/system/tests/modules/update_test_after/update_test_after.update_after.inc b/core/modules/system/tests/modules/update_test_after/update_test_after.update_after.inc
deleted file mode 100644
index b45197a..0000000
--- a/core/modules/system/tests/modules/update_test_after/update_test_after.update_after.inc
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-
-/**
- * First update.
- */
-function update_test_after_update_after_first() {
-  $execution = \Drupal::state()->get('update_test_after_execution', []);
-  $execution[] = __FUNCTION__;
-  \Drupal::state()->set('update_test_after_execution', $execution);
-}
-
-/**
- * Second update.
- */
-function update_test_after_update_after_second() {
-  $execution = \Drupal::state()->get('update_test_after_execution', []);
-  $execution[] = __FUNCTION__;
-  \Drupal::state()->set('update_test_after_execution', $execution);
-}
-
-/**
- * Test1 update.
- */
-function update_test_after_update_after_test1() {
-  $execution = \Drupal::state()->get('update_test_after_execution', []);
-  $execution[] = __FUNCTION__;
-  \Drupal::state()->set('update_test_after_execution', $execution);
-}
-
-/**
- * Test2 update.
- */
-function update_test_after_update_after_test0() {
-  $execution = \Drupal::state()->get('update_test_after_execution', []);
-  $execution[] = __FUNCTION__;
-  \Drupal::state()->set('update_test_after_execution', $execution);
-}
diff --git a/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.post_update.php b/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.post_update.php
new file mode 100644
index 0000000..7ff4945
--- /dev/null
+++ b/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.post_update.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * First update.
+ */
+function update_test_post_update_post_update_first() {
+  $execution = \Drupal::state()->get('post_update_test_execution', []);
+  $execution[] = __FUNCTION__;
+  \Drupal::state()->set('post_update_test_execution', $execution);
+}
+
+/**
+ * Second update.
+ */
+function update_test_post_update_post_update_second() {
+  $execution = \Drupal::state()->get('post_update_test_execution', []);
+  $execution[] = __FUNCTION__;
+  \Drupal::state()->set('post_update_test_execution', $execution);
+}
+
+/**
+ * Test1 update.
+ */
+function update_test_post_update_post_update_test1() {
+  $execution = \Drupal::state()->get('post_update_test_execution', []);
+  $execution[] = __FUNCTION__;
+  \Drupal::state()->set('post_update_test_execution', $execution);
+}
+
+/**
+ * Test2 update.
+ */
+function update_test_post_update_post_update_test0() {
+  $execution = \Drupal::state()->get('post_update_test_execution', []);
+  $execution[] = __FUNCTION__;
+  \Drupal::state()->set('post_update_test_execution', $execution);
+}
diff --git a/core/modules/system/tests/modules/update_test_after/update_test_after.info.yml b/core/modules/system/tests/modules/update_test_post_update/update_test_post_update.yml
similarity index 100%
rename from core/modules/system/tests/modules/update_test_after/update_test_after.info.yml
rename to core/modules/system/tests/modules/update_test_post_update/update_test_post_update.yml
diff --git a/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php b/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
index 92874ef..fe79330 100644
--- a/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Update/UpdateRegistryTest.php
@@ -28,7 +28,7 @@ class UpdateRegistryTest extends UnitTestCase {
   protected function setUp() {
     parent::setUp(); // TODO: Change the autogenerated stub
 
-    $settings = Settings::all();
+    $settings = [];
     $settings['extension_discovery_scan_tests'] = TRUE;
     new Settings($settings);
   }
@@ -55,13 +55,13 @@ protected function setupBasicModules() {
 /**
  * Module A update A.
  */
-function module_a_update_after_a() {
+function module_a_post_update_a() {
 }
 
 /**
  * Module A update B.
  */
-function module_a_update_after_b() {
+function module_a_post_update_b() {
 }
 
 EOS;
@@ -71,7 +71,7 @@ function module_a_update_after_b() {
 /**
  * Module B update A.
  */
-function module_b_update_after_a() {
+function module_b_post_update_a() {
 }
 
 EOS;
@@ -81,11 +81,11 @@ function module_b_update_after_a() {
         'default' => [
           'modules' => [
             'module_a' => [
-              'module_a.update_after.inc' => $module_a,
+              'module_a.post_update.php' => $module_a,
               'module_a.info.yml' => $info_a
             ],
             'module_b' => [
-              'module_b.update_after.inc' => $module_b,
+              'module_b.post_update.php' => $module_b,
               'module_b.info.yml' => $info_b
             ],
           ]
@@ -101,7 +101,7 @@ public function testGetMissingUpdateFunctionsWithNoExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__update_after', [])->wilLReturn([]);
+    $key_value->get('core.update__post_update', [])->wilLReturn([]);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -110,9 +110,9 @@ public function testGetMissingUpdateFunctionsWithNoExistingUpdates() {
     ], $key_value, FALSE);
 
     $this->assertEquals([
-      'module_a_update_after_a',
-      'module_a_update_after_b',
-      'module_b_update_after_a'
+      'module_a_post_update_a',
+      'module_a_post_update_b',
+      'module_b_post_update_a'
     ], $update_registry->getMissingUpdateFunctions());
   }
 
@@ -123,7 +123,7 @@ public function testGetMissingUpdateFunctionsWithExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__update_after', [])->wilLReturn(['module_a_update_after_a']);
+    $key_value->get('core.update__post_update', [])->wilLReturn(['module_a_post_update_a']);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -132,8 +132,8 @@ public function testGetMissingUpdateFunctionsWithExistingUpdates() {
     ], $key_value, FALSE);
 
     $this->assertEquals(array_values([
-      'module_a_update_after_b',
-      'module_b_update_after_a'
+      'module_a_post_update_b',
+      'module_b_post_update_a'
     ]), array_values($update_registry->getMissingUpdateFunctions()));
 
   }
@@ -145,7 +145,7 @@ public function testGetMissingUpdateList() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__update_after', [])->wilLReturn([]);
+    $key_value->get('core.update__post_update', [])->wilLReturn([]);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -154,10 +154,10 @@ public function testGetMissingUpdateList() {
     ], $key_value, FALSE);
 
     $expected = [];
-    $expected['module_a']['pending']['a'] = 'a - Module A update A.';
-    $expected['module_a']['pending']['b'] = 'b - Module A update B.';
+    $expected['module_a']['pending']['a'] = '<!-- function: module_a_post_update_a -->Module A update A.';
+    $expected['module_a']['pending']['b'] = '<!-- function: module_a_post_update_b -->Module A update B.';
     $expected['module_a']['start'] = 'a';
-    $expected['module_b']['pending']['a'] = 'a - Module B update A.';
+    $expected['module_b']['pending']['a'] = '<!-- function: module_b_post_update_a -->Module B update A.';
     $expected['module_b']['start'] = 'a';
 
     $this->assertEquals($expected, $update_registry->getMissingUpdateList());
@@ -170,7 +170,7 @@ public function testGetMissingUpdateListWithExistingUpdates() {
     $this->setupBasicModules();
 
     $key_value = $this->prophesize(KeyValueStoreInterface::class);
-    $key_value->get('core.update__update_after', [])->wilLReturn(['module_a_update_after_a']);
+    $key_value->get('core.update__post_update', [])->wilLReturn(['module_a_post_update_a']);
     $key_value = $key_value->reveal();
 
     $update_registry = new UpdateRegistry('vfs://drupal', 'sites/default', [
@@ -179,9 +179,9 @@ public function testGetMissingUpdateListWithExistingUpdates() {
     ], $key_value, FALSE);
 
     $expected = [];
-    $expected['module_a']['pending']['b'] = 'b - Module A update B.';
+    $expected['module_a']['pending']['b'] = '<!-- function: module_a_post_update_b -->Module A update B.';
     $expected['module_a']['start'] = 'b';
-    $expected['module_b']['pending']['a'] = 'a - Module B update A.';
+    $expected['module_b']['pending']['a'] = '<!-- function: module_b_post_update_a -->Module B update A.';
     $expected['module_b']['start'] = 'a';
 
     $this->assertEquals($expected, $update_registry->getMissingUpdateList());