diff --git a/js/leaflet.geocoder.js b/js/leaflet.geocoder.js
index a766796..5e2ed01 100644
--- a/js/leaflet.geocoder.js
+++ b/js/leaflet.geocoder.js
@@ -7,7 +7,7 @@
         let k = prefix ? prefix + "[" + p + "]" : p,
           v = obj[p];
         str.push((v !== null && typeof v === "object") ?
-          Drupal.Leaflet.query_url_serialize(v, k) :
+          Drupal.Leaflet.prototype.query_url_serialize(v, k) :
           encodeURIComponent(k) + "=" + encodeURIComponent(v));
       }
     }