diff --git a/simplesamlphp_auth.services.yml b/simplesamlphp_auth.services.yml
index d90cadc..43dcc3e 100644
--- a/simplesamlphp_auth.services.yml
+++ b/simplesamlphp_auth.services.yml
@@ -4,7 +4,7 @@ services:
     arguments: ['@config.factory', '@current_user', '@router.admin_context', '@module_handler', '@request_stack', '@messenger']
   simplesamlphp_auth.drupalauth:
     class: Drupal\simplesamlphp_auth\Service\SimplesamlphpDrupalAuth
-    arguments: ['@simplesamlphp_auth.manager', '@config.factory', '@entity_type.manager', '@logger.channel.simplesamlphp_auth', '@externalauth.externalauth', '@current_user']
+    arguments: ['@simplesamlphp_auth.manager', '@config.factory', '@entity_type.manager', '@logger.channel.simplesamlphp_auth', '@externalauth.externalauth', '@current_user', '@messenger', '@module_handler']
   simplesamlphp_auth_event_subscriber:
     class: Drupal\simplesamlphp_auth\EventSubscriber\SimplesamlSubscriber
     arguments: ['@simplesamlphp_auth.manager', '@current_user', '@config.factory', '@logger.channel.simplesamlphp_auth']
diff --git a/src/Service/SimplesamlphpDrupalAuth.php b/src/Service/SimplesamlphpDrupalAuth.php
index 6bdb8c5..7481c9b 100644
--- a/src/Service/SimplesamlphpDrupalAuth.php
+++ b/src/Service/SimplesamlphpDrupalAuth.php
@@ -8,13 +8,13 @@ use Drupal\user\UserInterface;
 use Drupal\Core\Session\AccountInterface;
 use Psr\Log\LoggerInterface;
 use Drupal\externalauth\ExternalAuthInterface;
-use Drupal\Core\Messenger\MessengerTrait;
+use Drupal\Core\Messenger\MessengerInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
 
 /**
  * Service to link SimpleSAMLphp authentication with Drupal users.
  */
 class SimplesamlphpDrupalAuth {
-  use MessengerTrait;
 
   /**
    * SimpleSAMLphp Authentication helper.
@@ -59,6 +59,20 @@ class SimplesamlphpDrupalAuth {
   protected $currentUser;
 
   /**
+   * The messenger.
+   *
+   * @var \Drupal\Core\Messenger\MessengerInterface
+   */
+  protected $messenger;
+
+  /**
+   * The module handler service.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
    * {@inheritdoc}
    *
    * @param SimplesamlphpAuthManager $simplesaml_auth
@@ -73,14 +87,20 @@ class SimplesamlphpDrupalAuth {
    *   The ExternalAuth service.
    * @param \Drupal\Core\Session\AccountInterface $account
    *   The currently logged in user.
+   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
+   *   The messenger.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
    */
-  public function __construct(SimplesamlphpAuthManager $simplesaml_auth, ConfigFactoryInterface $config_factory, EntityTypeManagerInterface $entity_type_manager, LoggerInterface $logger, ExternalAuthInterface $externalauth, AccountInterface $account) {
+  public function __construct(SimplesamlphpAuthManager $simplesaml_auth, ConfigFactoryInterface $config_factory, EntityTypeManagerInterface $entity_type_manager, LoggerInterface $logger, ExternalAuthInterface $externalauth, AccountInterface $account, MessengerInterface $messenger, ModuleHandlerInterface $module_handler) {
     $this->simplesamlAuth = $simplesaml_auth;
     $this->config = $config_factory->get('simplesamlphp_auth.settings');
     $this->entityTypeManager = $entity_type_manager;
     $this->logger = $logger;
     $this->externalauth = $externalauth;
     $this->currentUser = $account;
+    $this->messenger = $messenger;
+    $this->moduleHandler = $module_handler;
   }
 
   /**
@@ -129,8 +149,7 @@ class SimplesamlphpDrupalAuth {
 
       // We're not allowed to register new users on the site through simpleSAML.
       // We let the user know about this and redirect to the user/login page.
-      $this
-        ->messenger()
+      $this->messenger
         ->addMessage(t('We are sorry. While you have successfully authenticated, you are not yet entitled to access this site. Please ask the site administrator to provision access for you.'), 'status');
       $this->simplesamlAuth->logout(base_path());
 
@@ -161,8 +180,7 @@ class SimplesamlphpDrupalAuth {
         }
         // User is not permitted to login to Drupal via SAML.
         // Log out of SAML and redirect to the front page.
-        $this
-          ->messenger()
+        $this->messenger
           ->addMessage(t('We are sorry, your user account is not SAML enabled.'), 'status');
         $this->simplesamlAuth->logout(base_path());
         return FALSE;
@@ -175,8 +193,8 @@ class SimplesamlphpDrupalAuth {
         // Allow other modules to decide if there is an existing Drupal user,
         // based on the supplied SAML atttributes.
         $attributes = $this->simplesamlAuth->getAttributes();
-        foreach (\Drupal::moduleHandler()->getImplementations('simplesamlphp_auth_existing_user') as $module) {
-          $return_value = \Drupal::moduleHandler()->invoke($module, 'simplesamlphp_auth_existing_user', [$attributes]);
+        foreach ($this->moduleHandler->getImplementations('simplesamlphp_auth_existing_user') as $module) {
+          $return_value = $this->moduleHandler->invoke($module, 'simplesamlphp_auth_existing_user', [$attributes]);
           if ($return_value instanceof UserInterface) {
             $account = $return_value;
             if ($this->config->get('debug')) {
@@ -198,8 +216,7 @@ class SimplesamlphpDrupalAuth {
       }
       catch (\Exception $ex) {
         watchdog_exception('simplesamlphp_auth', $ex);
-        $this
-          ->messenger()
+        $this->messenger
           ->addMessage(t('Error registering user: An account with this username already exists.'), 'error');
       }
     }
@@ -232,9 +249,7 @@ class SimplesamlphpDrupalAuth {
           if ($this->currentUser->id() != $existing_account->id()) {
             $existing = TRUE;
             $this->logger->critical("Error on synchronizing name attribute for uid %new_uid: an account with the username %username and uid %existing_uid already exists.", ['%username' => $name, '%new_uid' => $this->currentUser->id(), '%existing_uid' => $existing_account->id()]);
-            $this
-              ->messenger()
-              ->addMessage(t('Error synchronizing username: an account with this username already exists.'), 'error');
+            $this->messenger->addMessage(t('Error synchronizing username: an account with this username already exists.'), 'error');
           }
         }
 
@@ -244,9 +259,7 @@ class SimplesamlphpDrupalAuth {
       }
       else {
         $this->logger->critical("Error on synchronizing name attribute: no username available for Drupal user %id.", ['%id' => $account->id()]);
-        $this
-          ->messenger()
-          ->addMessage(t('Error synchronizing username: no username is provided by SAML.'), 'error');
+        $this->messenger->addMessage(t('Error synchronizing username: no username is provided by SAML.'), 'error');
       }
     }
 
@@ -257,9 +270,7 @@ class SimplesamlphpDrupalAuth {
       }
       else {
         $this->logger->critical("Error on synchronizing mail attribute: no email address available for Drupal user %id.", ['%id' => $account->id()]);
-        $this
-          ->messenger()
-          ->addMessage(t('Error synchronizing mail: no email address is provided by SAML.'), 'error');
+        $this->messenger->addMessage(t('Error synchronizing mail: no email address is provided by SAML.'), 'error');
       }
     }
 
@@ -322,7 +333,7 @@ class SimplesamlphpDrupalAuth {
     }
 
     $attributes = $this->simplesamlAuth->getAttributes();
-    \Drupal::modulehandler()->alter('simplesamlphp_auth_user_roles', $roles, $attributes);
+    $this->moduleHandler->alter('simplesamlphp_auth_user_roles', $roles, $attributes);
     return $roles;
   }