diff --git a/src/Plugin/Field/FieldFormatter/PrivateMessageThreadMemberFormatter.php b/src/Plugin/Field/FieldFormatter/PrivateMessageThreadMemberFormatter.php
index b8b7817..583d6f5 100644
--- a/src/Plugin/Field/FieldFormatter/PrivateMessageThreadMemberFormatter.php
+++ b/src/Plugin/Field/FieldFormatter/PrivateMessageThreadMemberFormatter.php
@@ -11,6 +11,8 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\Core\Session\AccountProxyInterface;
 use Drupal\Core\Url;
+use Drupal\user\Entity\User;
+use Drupal\user\UserInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -173,6 +175,11 @@ class PrivateMessageThreadMemberFormatter extends FormatterBase implements Conta
     $view_builder = $this->entityManager->getViewBuilder('user');
     foreach ($items as $delta => $item) {
       $user = $item->entity;
+
+      if (!$user instanceof UserInterface) {
+        continue;
+      }
+
       if ($user->id() != $this->currentUser->id()) {
         if ($this->getSetting('display_type') == 'label') {
           if ($access_profiles) {