diff --git a/lib/cartodb/models/mapconfig/adapter/mapconfig-overviews-adapter.js b/lib/cartodb/models/mapconfig/adapter/mapconfig-overviews-adapter.js
index 06b67b64..4134b19f 100644
--- a/lib/cartodb/models/mapconfig/adapter/mapconfig-overviews-adapter.js
+++ b/lib/cartodb/models/mapconfig/adapter/mapconfig-overviews-adapter.js
@@ -60,8 +60,8 @@ MapConfigOverviewsAdapter.prototype.getMapConfig = function (user, requestMapCon
                             query_rewrite_data.filter_stats = stats;
 
                             if (!_.isEmpty(metadata)) {
-                                layer = _.extend({}, layer);
-                                layer.options = _.extend({}, layer.options, { query_rewrite_data: query_rewrite_data });
+                                layer = Object.assign({}, layer);
+                                layer.options = Object.assign({}, layer.options, { query_rewrite_data });
                             }
 
                             return done(null, layer);
@@ -69,8 +69,8 @@ MapConfigOverviewsAdapter.prototype.getMapConfig = function (user, requestMapCon
                     );
                 } else {
                     if (!_.isEmpty(metadata)) {
-                        layer = _.extend({}, layer);
-                        layer.options = _.extend({}, layer.options, { query_rewrite_data: query_rewrite_data });
+                        layer = Object.assign({}, layer);
+                        layer.options = Object.assign({}, layer.options, { query_rewrite_data });
                     }
 
                     return done(null, layer);