diff --git a/wagtail/contrib/postgres_search/backend.py b/wagtail/contrib/postgres_search/backend.py
index a824a5ef66..30b14317a1 100644
--- a/wagtail/contrib/postgres_search/backend.py
+++ b/wagtail/contrib/postgres_search/backend.py
@@ -168,10 +168,10 @@ class Index(object):
             obj._object_id = force_text(obj.pk)
             obj._body_ = self.prepare_body(obj)
         connection = connections[self.db_alias]
-        # if connection.pg_version >= 90500:  # PostgreSQL >= 9.5
-        #     self.add_items_upsert(connection, content_type_pk, objs, config)
-        # else:
-        self.add_items_update_then_create(content_type_pk, objs, config)
+        if connection.pg_version >= 90500:  # PostgreSQL >= 9.5
+            self.add_items_upsert(connection, content_type_pk, objs, config)
+        else:
+            self.add_items_update_then_create(content_type_pk, objs, config)
 
     def __str__(self):
         return self.name
@@ -331,7 +331,7 @@ class PostgresSearchBackend(BaseSearchBackend):
             self.get_index_for_object(obj_list[0]).add_items(model, obj_list)
 
     def delete(self, obj):
-        obj.index_entries.delete()
+        obj.index_entries.all().delete()
 
 
 SearchBackend = PostgresSearchBackend