diff --git a/src/ol/tile/openstreetmap.js b/src/ol/tile/openstreetmap.js
index 8d2b95919a..b4397a0743 100644
--- a/src/ol/tile/openstreetmap.js
+++ b/src/ol/tile/openstreetmap.js
@@ -20,8 +20,6 @@ ol.tilelayer.createOpenStreetMap = function(opt_values) {
       '© ' +
       '<a href="http://www.openstreetmap.org">OpenStreetMap</a> ' +
       'contributors, ' +
-      '<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC BY-SA</a>',
-      ''
-      );
+      '<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC BY-SA</a>');
   return new ol.TileLayer(store, opt_values);
 };
diff --git a/src/ol/tile/tile.js b/src/ol/tile/tile.js
index 6ab24d6244..f326daab8d 100644
--- a/src/ol/tile/tile.js
+++ b/src/ol/tile/tile.js
@@ -24,9 +24,9 @@ ol.TileLoadState = {
  * @extends {goog.events.EventTarget}
  * @param {ol.TileCoord} tileCoord Tile coordinate.
  * @param {string} src Source.
- * @param {string=} opt_crossOrigin Cross origin.
+ * @param {?string} crossOrigin Cross origin.
  */
-ol.Tile = function(tileCoord, src, opt_crossOrigin) {
+ol.Tile = function(tileCoord, src, crossOrigin) {
 
   goog.base(this);
 
@@ -52,8 +52,8 @@ ol.Tile = function(tileCoord, src, opt_crossOrigin) {
    * @type {Image}
    */
   this.image_ = new Image();
-  if (goog.isDef(opt_crossOrigin)) {
-    this.image_.crossOrigin = opt_crossOrigin;
+  if (!goog.isNull(crossOrigin)) {
+    this.image_.crossOrigin = crossOrigin;
   }
 
   /**
diff --git a/src/ol/tile/tilestore.js b/src/ol/tile/tilestore.js
index 0be1f12b76..b4f7a58c3d 100644
--- a/src/ol/tile/tilestore.js
+++ b/src/ol/tile/tilestore.js
@@ -16,7 +16,7 @@ goog.require('ol.TileUrlFunctionType');
  * @param {ol.TileUrlFunctionType} tileUrlFunction Tile URL.
  * @param {ol.Extent=} opt_extent Extent.
  * @param {string=} opt_attribution Attribution.
- * @param {string=} opt_crossOrigin Cross origin.
+ * @param {?string=} opt_crossOrigin Cross origin.
  */
 ol.TileStore = function(projection, tileGrid, tileUrlFunction, opt_extent,
     opt_attribution, opt_crossOrigin) {
@@ -37,9 +37,10 @@ ol.TileStore = function(projection, tileGrid, tileUrlFunction, opt_extent,
 
   /**
    * @private
-   * @type {string|undefined}
+   * @type {?string}
    */
-  this.crossOrigin_ = opt_crossOrigin;
+  this.crossOrigin_ =
+      goog.isDef(opt_crossOrigin) ? opt_crossOrigin : 'anonymous';
 
   /**
    * @private