diff --git a/cubicweb_elasticsearch/entities.py b/cubicweb_elasticsearch/entities.py
index e94a0c1044060760bd99356036f22eee109752da_Y3ViaWN3ZWJfZWxhc3RpY3NlYXJjaC9lbnRpdGllcy5weQ==..9d0bba1e08cafa909fdc4f36555e6abfd05ac391_Y3ViaWN3ZWJfZWxhc3RpY3NlYXJjaC9lbnRpdGllcy5weQ== 100644
--- a/cubicweb_elasticsearch/entities.py
+++ b/cubicweb_elasticsearch/entities.py
@@ -221,7 +221,7 @@
         if self._cw.deleted_in_transaction(entity.eid):
             es_method = indexer.es_delete
         elif es_operation['op_type'] == 'index':
-            es_method = partial(indexer.es_index, params={'refresh': True})
+            es_method = partial(indexer.es_index, params={'refresh': 'true'})
         elif es_operation['op_type'] == 'delete':
             es_method = indexer.es_delete
         else: