diff --git a/core/includes/update.inc b/core/includes/update.inc
index 7cacba384d3a1d75a7df84632fd86bf51cb4d961..4b45b27b65f1a65603d5ab33ebea8ca02dcd4349 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -9,38 +9,8 @@
  */
 
 use Drupal\Component\Graph\Graph;
-use Drupal\Core\Update\UpdateKernel;
 use Drupal\Core\Utility\Error;
 
-/**
- * Disables any extensions that are incompatible with the current core version.
- *
- * @deprecated in Drupal 8.8.4 and is removed from Drupal 9.0.0.
- *
- * @see https://www.drupal.org/node/3026100
- */
-function update_fix_compatibility() {
-  @trigger_error(__FUNCTION__ . '() is deprecated in Drupal 8.8.4 and will be removed before Drupal 9.0.0. There is no replacement. See https://www.drupal.org/node/3026100', E_USER_DEPRECATED);
-  // Fix extension objects if the update is being done via Drush 8. In non-Drush
-  // environments this will already be fixed by the UpdateKernel this point.
-  UpdateKernel::fixSerializedExtensionObjects(\Drupal::getContainer());
-
-  $extension_config = \Drupal::configFactory()->getEditable('core.extension');
-  $save = FALSE;
-  foreach (['module', 'theme'] as $type) {
-    foreach ($extension_config->get($type) as $name => $weight) {
-      if (update_check_incompatibility($name, $type)) {
-        $extension_config->clear("$type.$name");
-        $save = TRUE;
-      }
-    }
-  }
-  if ($save) {
-    $extension_config->set('module', module_config_sort($extension_config->get('module')));
-    $extension_config->save();
-  }
-}
-
 /**
  * Tests the compatibility of a module or theme.
  */
diff --git a/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php b/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php
deleted file mode 100644
index eb51f496898b0e63b1da7a560de9f2ad323dbb08..0000000000000000000000000000000000000000
--- a/core/tests/Drupal/KernelTests/Core/Update/CompatibilityFixTest.php
+++ /dev/null
@@ -1,53 +0,0 @@
-<?php
-
-namespace Drupal\KernelTests\Core\Update;
-
-use Drupal\KernelTests\KernelTestBase;
-
-/**
- * Tests that extensions that are incompatible with the current core version are disabled.
- *
- * @group Update
- * @group legacy
- */
-class CompatibilityFixTest extends KernelTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static $modules = ['system'];
-
-  protected function setUp(): void {
-    parent::setUp();
-    require_once $this->root . '/core/includes/update.inc';
-  }
-
-  /**
-   * @expectedDeprecation update_fix_compatibility() is deprecated in Drupal 8.8.4 and will be removed before Drupal 9.0.0. There is no replacement. See https://www.drupal.org/node/3026100
-   */
-  public function testFixCompatibility() {
-    $extension_config = \Drupal::configFactory()->getEditable('core.extension');
-
-    // Add an incompatible/non-existent module to the config.
-    $modules = $extension_config->get('module');
-    $modules['incompatible_module'] = 0;
-    $extension_config->set('module', $modules);
-    $modules = $extension_config->get('module');
-    $this->assertTrue(in_array('incompatible_module', array_keys($modules)), 'Added incompatible/non-existent module to the config.');
-
-    // Add an incompatible/non-existent theme to the config.
-    $themes = $extension_config->get('theme');
-    $themes['incompatible_theme'] = 0;
-    $extension_config->set('theme', $themes);
-    $themes = $extension_config->get('theme');
-    $this->assertTrue(in_array('incompatible_theme', array_keys($themes)), 'Added incompatible/non-existent theme to the config.');
-
-    // Fix compatibility.
-    update_fix_compatibility();
-    $modules = $extension_config->get('module');
-    $this->assertFalse(in_array('incompatible_module', array_keys($modules)), 'Fixed modules compatibility.');
-    $themes = $extension_config->get('theme');
-    $this->assertFalse(in_array('incompatible_theme', array_keys($themes)), 'Fixed themes compatibility.');
-  }
-
-}