diff --git a/src/ol/source/tilejson.js b/src/ol/source/tilejson.js
index d705320993..35c9124468 100644
--- a/src/ol/source/tilejson.js
+++ b/src/ol/source/tilejson.js
@@ -17,6 +17,7 @@ goog.require('ol.Projection');
 goog.require('ol.TileCoverageArea');
 goog.require('ol.TileUrlFunction');
 goog.require('ol.source.TileSource');
+goog.require('ol.tilegrid.XYZ');
 
 
 /**