diff -u b/src/DefaultContentManager.php b/src/DefaultContentManager.php
--- b/src/DefaultContentManager.php
+++ b/src/DefaultContentManager.php
@@ -7,6 +7,8 @@
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Entity\EntityRepositoryInterface;
+use Drupal\Core\Entity\RevisionableInterface;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Extension\InfoParserInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Session\AccountInterface;
@@ -118,7 +120,7 @@
    *   The serializer service.
    * @param \Drupal\rest\Plugin\Type\ResourcePluginManager $resource_plugin_manager
    *   The rest resource plugin manager.
-   * @param \Drupal\Core\Session|AccountInterface $current_user
+   * @param \Drupal\Core\Session\AccountInterface $current_user
    *   The current user.
    * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_manager
    *   The entity type manager service.
@@ -147,7 +149,7 @@
   /**
    * {@inheritdoc}
    */
-  public function importContent($module) {
+  public function importContent($module, $update_existing = FALSE) {
     $created = array();
     $folder = drupal_get_path('module', $module) . "/content";
 
@@ -219,19 +221,31 @@
           $contents = $this->parseFile($file);
           $class = $definition['serialization_class'];
           $entity = $this->serializer->deserialize($contents, $class, 'hal_json', array('request_method' => 'POST'));
+          $is_new = TRUE;
+
+          // Allow existing entities overwrite.
           if ($old_entity = $this->entityRepository->loadEntityByUuid($entity_type_id, $entity->uuid())) {
-            $entity->{$entity->getEntityType()->getKey('id')} = $old_entity->id();
-            $entity->setOriginalId($old_entity->id());
-            $entity->enforceIsNew(FALSE);
-            try {
-              $entity->setNewRevision(FALSE);
-            } catch (\LogicException $e) {}
+            if ($update_existing) {
+              $original_id = $old_entity->id();
+              $entity->{$entity->getEntityType()->getKey('id')} = $original_id;
+              $is_new = FALSE;
+              if ($this->isRevisionableEntity($entity)) {
+                $entity->setNewRevision(FALSE);
+              }
+            }
           }
           else {
-            $entity->enforceIsNew(TRUE);
+            if ($this->isRevisionableEntity($entity)) {
+              $entity->setNewRevision(TRUE);
+            }
+          }
+
+          $is_new ? $entity->setOriginalId($original_id) : $entity->enforceIsNew($is_new);
+
+          if (!$old_entity || $update_existing) {
+            $entity->save();
+            $created[$entity->uuid()] = $entity;
           }
-          $entity->save();
-          $created[$entity->uuid()] = $entity;
         }
       }
       $this->eventDispatcher->dispatch(DefaultContentEvents::IMPORT, new ImportEvent($created, $module));
@@ -244,6 +258,19 @@
   }
 
   /**
+   * Checks a given entity for revision support.
+   *
+   * @param EntityInterface $entity
+   *   A typical drupal entity object.
+   *
+   * @return bool
+   *   Whether this entity supports revisions.
+   */
+  public function isRevisionableEntity(EntityInterface $entity) {
+    return $entity instanceof RevisionableInterface && $entity->getEntityType()->isRevisionable();
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function exportContent($entity_type_id, $entity_id) {
only in patch2:
unchanged:
--- a/src/DefaultContentManagerInterface.php
+++ b/src/DefaultContentManagerInterface.php
@@ -20,11 +20,13 @@ interface DefaultContentManagerInterface {
    *
    * @param string $module
    *   The module to create the default content for.
+   * @param bool $update_existing
+   *   (optional) Force updating existing entities. Defaults to FALSE.
    *
    * @return array[\Drupal\Core\Entity\EntityInterface]
    *   The created entities.
    */
-  public function importContent($module);
+  public function importContent($module, $update_existing = FALSE);
 
   /**
    * Exports a single entity as importContent expects it.