diff --git a/src/ol/tileurlfunction.js b/src/ol/tileurlfunction.js
index 66fb2998f9..0989c5eb79 100644
--- a/src/ol/tileurlfunction.js
+++ b/src/ol/tileurlfunction.js
@@ -1,5 +1,6 @@
 goog.provide('ol.TileUrlFunction');
 
+goog.require('ol');
 goog.require('ol.asserts');
 goog.require('ol.math');
 goog.require('ol.tilecoord');