diff --git a/DependencyInjection/ONGRElasticsearchExtension.php b/DependencyInjection/ONGRElasticsearchExtension.php
index a42172b4..638b8857 100644
--- a/DependencyInjection/ONGRElasticsearchExtension.php
+++ b/DependencyInjection/ONGRElasticsearchExtension.php
@@ -44,7 +44,7 @@ public function load(array $configs, ContainerBuilder $container)
 
         $managers = $config['managers'];
         foreach ($managers as &$manager) {
-            $manager['mappings'] = array_unique($manager['mappings']);
+            $manager['mappings'] = array_unique($manager['mappings'], SORT_REGULAR);
         }
         $container->setParameter('es.cache', $config['cache']);
         $container->setParameter('es.analysis', $config['analysis']);