diff --git a/app/assets/javascripts/discourse/components/date-picker.js.es6 b/app/assets/javascripts/discourse/components/date-picker.js.es6
index 621b0d1fd81..53b7c0c4249 100644
--- a/app/assets/javascripts/discourse/components/date-picker.js.es6
+++ b/app/assets/javascripts/discourse/components/date-picker.js.es6
@@ -28,7 +28,7 @@ export default Em.Component.extend({
         onSelect: date => this.set("value", moment(date).format("YYYY-MM-DD"))
       };
 
-      this._picker = new Pikaday(Object.assign(default_opts, this._opts()));
+      this._picker = new Pikaday(_.merge(default_opts, this._opts()));
     });
   },