diff --git a/src/ol/tileurlfunction.js b/src/ol/tileurlfunction.js
index d2d348a7e0..d69080dc0a 100644
--- a/src/ol/tileurlfunction.js
+++ b/src/ol/tileurlfunction.js
@@ -14,6 +14,12 @@ goog.require('ol.extent');
 ol.TileUrlFunctionType;
 
 
+/**
+ * @typedef {function(ol.TileCoord, ol.Projection, ol.TileCoord=): ol.TileCoord}
+ */
+ol.TileCoordTransformType;
+
+
 /**
  * @param {string} template Template.
  * @return {ol.TileUrlFunctionType} Tile URL function.
@@ -121,8 +127,7 @@ ol.TileUrlFunction.nullTileUrlFunction = function(tileCoord, projection) {
 
 
 /**
- * @param {function(ol.TileCoord, ol.Projection, ol.TileCoord=): ol.TileCoord}
- *     transformFn Transform function.
+ * @param {ol.TileCoordTransformType} transformFn Transform function.
  * @param {ol.TileUrlFunctionType} tileUrlFunction Tile URL function.
  * @return {ol.TileUrlFunctionType} Tile URL function.
  */