diff --git a/src/ol/layer/tilelayer.js b/src/ol/layer/tilelayer.js
index 54c5262050..3d59d3427a 100644
--- a/src/ol/layer/tilelayer.js
+++ b/src/ol/layer/tilelayer.js
@@ -1,6 +1,7 @@
 goog.provide('ol.layer.Tile');
 
 goog.require('goog.object');
+goog.require('ol');
 goog.require('ol.layer.Layer');
 
 
@@ -29,7 +30,7 @@ ol.layer.TileProperty = {
  * @api stable
  */
 ol.layer.Tile = function(opt_options) {
-  var options = goog.isDef(opt_options) ? opt_options : {};
+  var options = opt_options ? opt_options : {};
 
   var baseOptions = goog.object.clone(options);
 
@@ -37,9 +38,10 @@ ol.layer.Tile = function(opt_options) {
   delete baseOptions.useInterimTilesOnError;
   goog.base(this,  /** @type {olx.layer.LayerOptions} */ (baseOptions));
 
-  this.setPreload(goog.isDef(options.preload) ? options.preload : 0);
-  this.setUseInterimTilesOnError(goog.isDef(options.useInterimTilesOnError) ?
-      options.useInterimTilesOnError : true);
+  this.setPreload(ol.isDef(options.preload) ?
+      /** @type {number} */ (options.preload) : 0);
+  this.setUseInterimTilesOnError(ol.isDef(options.useInterimTilesOnError) ?
+      /** @type {boolean} */ (options.useInterimTilesOnError) : true);
 };
 goog.inherits(ol.layer.Tile, ol.layer.Layer);