diff --git a/src/ol/structs/rbush.js b/src/ol/structs/rbush.js
index 3f1b20dea8..b84554ac7c 100644
--- a/src/ol/structs/rbush.js
+++ b/src/ol/structs/rbush.js
@@ -540,7 +540,7 @@ ol.structs.RBush.prototype.getExtent = function(opt_extent) {
  */
 ol.structs.RBush.prototype.getKey_ = function(value) {
   goog.asserts.assert(goog.isObject(value));
-  return goog.getUid(value) + '';
+  return goog.getUid(value).toString();
 };
 
 
diff --git a/src/ol/tileurlfunction.js b/src/ol/tileurlfunction.js
index 008e609f39..d193383766 100644
--- a/src/ol/tileurlfunction.js
+++ b/src/ol/tileurlfunction.js
@@ -37,9 +37,9 @@ ol.TileUrlFunction.createFromTemplate = function(template) {
         if (goog.isNull(tileCoord)) {
           return undefined;
         } else {
-          return template.replace('{z}', '' + tileCoord.z)
-                         .replace('{x}', '' + tileCoord.x)
-                         .replace('{y}', '' + tileCoord.y);
+          return template.replace('{z}', tileCoord.z.toString())
+                         .replace('{x}', tileCoord.x.toString())
+                         .replace('{y}', tileCoord.y.toString());
         }
       });
 };