diff --git a/core/lib/Drupal/Core/Entity/ContentEntityNullStorage.php b/core/lib/Drupal/Core/Entity/ContentEntityNullStorage.php
index 837ff1a..6236520 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityNullStorage.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityNullStorage.php
@@ -84,6 +84,12 @@ protected function getQueryServiceName() {
   /**
    * {@inheritdoc}
    */
+  protected function doLoadRevisionFieldItems($revision_id) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   protected function doSaveFieldItems(ContentEntityInterface $entity, array $names = []) {
   }
 
diff --git a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
index b1da527..95bc44e 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php
@@ -187,7 +187,7 @@ public function loadRevision($revision_id) {
     $revision = $this->doLoadRevisionFieldItems($revision_id);
 
     if ($revision) {
-      $entities = [$revision];
+      $entities = [$revision->id() => $revision];
       $this->invokeStorageLoadHook($entities);
       $this->postLoad($entities);
     }
@@ -198,11 +198,11 @@ public function loadRevision($revision_id) {
   /**
    * Actually loads revision field item values from the storage.
    *
-   * @param int $revision_id
+   * @param int|string $revision_id
    *   The revision identifier.
    *
-   * @return \Drupal\Core\Entity\ContentEntityInterface|null
-   *   The re
+   * @return \Drupal\Core\Entity\EntityInterface|null
+   *   The specified entity revision or NULL if not found.
    */
   abstract protected function doLoadRevisionFieldItems($revision_id);
 
diff --git a/core/lib/Drupal/Core/Entity/EntityStorageInterface.php b/core/lib/Drupal/Core/Entity/EntityStorageInterface.php
index 98cd4b4..f7b4b4a 100644
--- a/core/lib/Drupal/Core/Entity/EntityStorageInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityStorageInterface.php
@@ -79,7 +79,7 @@ public function loadUnchanged($id);
   /**
    * Load a specific entity revision.
    *
-   * @param int $revision_id
+   * @param int|string $revision_id
    *   The revision id.
    *
    * @return \Drupal\Core\Entity\EntityInterface|null