diff -u b/core/lib/Drupal/Core/Entity/ContentUninstallValidator.php b/core/lib/Drupal/Core/Entity/ContentUninstallValidator.php
--- b/core/lib/Drupal/Core/Entity/ContentUninstallValidator.php
+++ b/core/lib/Drupal/Core/Entity/ContentUninstallValidator.php
@@ -29,7 +29,7 @@
   public function validate($module) {
     $entities = $this->entityManager->getDefinitions();
     foreach ($entities as $entity_type) {
-      if ($module == $entity_type->getProvider() && is_subclass_of($entity_type->getClass(), 'Drupal\Core\Entity\ContentEntityInterface') && $this->entityManager->getStorage($entity_type->id())->hasData()) {
+      if ($module == $entity_type->getProvider() && $entity_type instanceof ContentEntityTypeInterface && $this->entityManager->getStorage($entity_type->id())->hasData()) {
         return FALSE;
       }
     }