diff --git a/lib/AutoGroupsManager.php b/lib/AutoGroupsManager.php
index cb0fabc..2db5020 100644
--- a/lib/AutoGroupsManager.php
+++ b/lib/AutoGroupsManager.php
@@ -25,31 +25,29 @@
 
 namespace OCA\AutoGroups;
 
+use OCP\AppFramework\OCS\OCSBadRequestException;
+use OCP\EventDispatcher\Event;
 use OCP\IGroupManager;
 use OCP\IConfig;
 use OCP\IL10N;
-
-use OCP\AppFramework\OCS\OCSBadRequestException;
+use OCP\IUserManager;
 
 use Psr\Log\LoggerInterface;
 
 class AutoGroupsManager
 {
-    private $groupManager;
-    private $logger;
-    private $config;
-    private $l;
 
     /**
      * AutoGroupsManager constructor.
      */
-    public function __construct(IGroupManager $groupManager, IConfig $config, LoggerInterface $logger, IL10N $l)
+    public function __construct(
+		private readonly IGroupManager $groupManager,
+		private readonly IUserManager $userManager,
+		private readonly IConfig $config,
+		private readonly LoggerInterface $logger,
+		private readonly IL10N $l,
+	)
     {
-        $this->groupManager = $groupManager;
-        $this->logger = $logger;
-        $this->config = $config;
-        $this->l = $l;
-
         // Migrate old config if necessary
         $creationOnly = $this->config->getAppValue("AutoGroups", "creation_only");
         if ($creationOnly !== '') {
@@ -92,7 +90,7 @@ public function __construct(IGroupManager $groupManager, IConfig $config, Logger
     /**
      * The event handler to check group assignment for a user
      */
-    public function addAndRemoveAutoGroups($event)
+    public function addAndRemoveAutoGroups(Event $event): void
     {
         // Get configuration
         $groupNames = json_decode($this->config->getAppValue("auto_groups", "auto_groups", '[]'));
@@ -100,6 +98,13 @@ public function addAndRemoveAutoGroups($event)
 
         // Get user information
         $user = $event->getUser();
+
+		if (!$this->userManager->userExists($user->getUID())) {
+			// Avoid doing any group manipulation when running inside
+			// OC\User\BackgroundJobs\CleanupDeletedUsers
+			return;
+		}
+
         $userGroupNames = $this->groupManager->getUserGroupIds($user);
 
         // Notice message for Auto Group Hook Execution
diff --git a/tests/Unit/AutoGroupsManagerTest.php b/tests/Unit/AutoGroupsManagerTest.php
index 0ee1378..6d5b29b 100644
--- a/tests/Unit/AutoGroupsManagerTest.php
+++ b/tests/Unit/AutoGroupsManagerTest.php
@@ -25,6 +25,7 @@
 namespace OCA\AutoGroups\Tests\Unit;
 
 use OCP\Group\Events\BeforeGroupDeletedEvent;
+use OCP\IUserManager;
 use OCP\User\Events\UserCreatedEvent;
 
 use OCP\IGroupManager;
@@ -38,6 +39,7 @@
 
 use OCA\AutoGroups\AutoGroupsManager;
 
+use PHPUnit\Framework\MockObject\MockObject;
 use Psr\Log\LoggerInterface;
 
 use Test\TestCase;
@@ -45,27 +47,31 @@
 
 class AutoGroupsManagerTest extends TestCase
 {
-    private $groupManager;
-    private $config;
-    private $logger;
-    private $il10n;
+    private IGroupManager&MockObject $groupManager;
+	private IUserManager&MockObject $userManager;
+    private IConfig&MockObject $config;
+    private LoggerInterface&MockObject $logger;
+    private IL10N&MockObject $il10n;
 
     protected function setUp(): void
     {
         parent::setUp();
 
         $this->groupManager = $this->createMock(IGroupManager::class);
+		$this->userManager = $this->createMock(IUserManager::class);
         $this->config = $this->createMock(IConfig::class);
         $this->logger = $this->createMock(LoggerInterface::class);
         $this->il10n = $this->createMock(IL10N::class);
 
+		$this->userManager->method('userExists')->willReturn(true);
+
         $this->testUser = $this->createMock(IUser::class);
         $this->testUser->expects($this->any())
             ->method('getDisplayName')
             ->willReturn('Test User');
     }
 
-    private function createAutoGroupsManager($auto_groups = [], $override_groups = [])
+    private function createAutoGroupsManager($auto_groups = [], $override_groups = []): AutoGroupsManager
     {
         $this->config->method('getAppValue')
             ->willReturnCallback(function ($app, $key, $default = '') use ($auto_groups, $override_groups) {
@@ -81,10 +87,10 @@ private function createAutoGroupsManager($auto_groups = [], $override_groups = [
                 return $default;
             });
 
-        return new AutoGroupsManager($this->groupManager, $this->config, $this->logger, $this->il10n);
+        return new AutoGroupsManager($this->groupManager, $this->userManager, $this->config, $this->logger, $this->il10n);
     }
 
-    private function configMigrationTestImpl($creationOnly, $expectedModification)
+    private function configMigrationTestImpl($creationOnly, $expectedModification): AutoGroupsManager
     {
         $this->config->expects($this->exactly(2))
             ->method('getAppValue')
@@ -102,7 +108,7 @@ private function configMigrationTestImpl($creationOnly, $expectedModification)
             ->method('deleteAppValue')
             ->with('AutoGroups', 'creation_only');
 
-        return new AutoGroupsManager($this->groupManager, $this->config, $this->logger, $this->il10n);
+        return new AutoGroupsManager($this->groupManager, $this->userManager, $this->config, $this->logger, $this->il10n);
     }
 
     public function testAddingToAutoGroups()