diff --git a/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php b/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
index afca009..eb79f62 100644
--- a/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
+++ b/core/lib/Drupal/Core/Entity/FieldableDatabaseStorageController.php
@@ -637,10 +637,15 @@ public function save(EntityInterface $entity) {
         // Ensure the entity is still seen as new after assigning it an id,
         // while storing its data.
         $entity->enforceIsNew();
-        $values[$this->idKey] = $this->database
+        $insert_id = $this->database
           ->insert($this->baseTable, array('return' => Database::RETURN_INSERT_ID))
           ->fields($values)
           ->execute();
+        // Even if this is a new entity, the ID key might have been set in which
+        // case we should not override the provided ID.
+        if (!isset($values[$this->idKey])) {
+          $values[$this->idKey] = $insert_id;
+        }
         $return = SAVED_NEW;
         $entity->{$this->idKey}->value = (string) $values[$this->idKey];
         if ($this->revisionTable) {
@@ -810,10 +815,15 @@ protected function saveRevision(ContentEntityInterface $entity) {
     $entity->preSaveRevision($this, $values);
 
     if ($entity->isNewRevision()) {
-      $values[$this->revisionKey] = $this->database
+      $insert_id = $this->database
         ->insert($this->revisionTable, array('return' => Database::RETURN_INSERT_ID))
         ->fields($values)
         ->execute();
+      // Even if this is a new revsision, the revision ID key might have been
+      // set in which case we should not override the provided revision ID.
+      if (!isset($values[$this->revisionKey])) {
+        $values[$this->revisionKey] = $insert_id;;
+      }
       if ($entity->isDefaultRevision()) {
         $this->database->update($this->entityType->getBaseTable())
           ->fields(array($this->revisionKey => $values[$this->revisionKey]))