diff -u b/core/lib/Drupal/Core/Entity/Schema/EntitySchemaManager.php b/core/lib/Drupal/Core/Entity/Schema/EntitySchemaManager.php
--- b/core/lib/Drupal/Core/Entity/Schema/EntitySchemaManager.php
+++ b/core/lib/Drupal/Core/Entity/Schema/EntitySchemaManager.php
@@ -164,7 +164,7 @@
    */
   public function onEntityTypeCreate(EntityTypeInterface $entity_type) {
     $this->saveEntityTypeDefinition($entity_type);
-    if (($entity_type instanceof ContentEntityTypeInterface) && $entity_type->isFieldable()) {
+    if ($entity_type->isFieldable()) {
       $entity_type_id = $entity_type->id();
       $this->saveFieldStorageDefinitions($entity_type_id, $this->entityManager->getFieldStorageDefinitions($entity_type_id));
     }