diff --git a/src/ol/layer/imagelayer.js b/src/ol/layer/imagelayer.js
index d75edf8ded..9f8d1bf4e3 100644
--- a/src/ol/layer/imagelayer.js
+++ b/src/ol/layer/imagelayer.js
@@ -1,7 +1,6 @@
 goog.provide('ol.layer.Image');
 
 goog.require('ol.layer.Layer');
-goog.require('ol.source.Image');
 
 
 
@@ -15,11 +14,3 @@ ol.layer.Image = function(options) {
   goog.base(this, options);
 };
 goog.inherits(ol.layer.Image, ol.layer.Layer);
-
-
-/**
- * @return {ol.source.Image} Single image source.
- */
-ol.layer.Image.prototype.getImageSource = function() {
-  return /** @type {ol.source.Image} */ (this.getSource());
-};
diff --git a/src/ol/renderer/canvas/canvasimagelayerrenderer.js b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
index da68e20e4b..da01e396aa 100644
--- a/src/ol/renderer/canvas/canvasimagelayerrenderer.js
+++ b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
@@ -10,6 +10,7 @@ goog.require('ol.ViewHint');
 goog.require('ol.layer.Image');
 goog.require('ol.renderer.Map');
 goog.require('ol.renderer.canvas.Layer');
+goog.require('ol.source.Image');
 
 
 
@@ -70,7 +71,8 @@ ol.renderer.canvas.ImageLayer.prototype.renderFrame =
   var image;
   var imageLayer = this.getLayer();
   goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
-  var imageSource = imageLayer.getImageSource();
+  var imageSource = imageLayer.getSource();
+  goog.asserts.assertInstanceof(imageSource, ol.source.Image);
 
   var hints = frameState.viewHints;
 
diff --git a/src/ol/renderer/dom/domimagelayerrenderer.js b/src/ol/renderer/dom/domimagelayerrenderer.js
index cc5843b453..7d6be8b57a 100644
--- a/src/ol/renderer/dom/domimagelayerrenderer.js
+++ b/src/ol/renderer/dom/domimagelayerrenderer.js
@@ -12,6 +12,7 @@ goog.require('ol.ViewHint');
 goog.require('ol.dom');
 goog.require('ol.layer.Image');
 goog.require('ol.renderer.dom.Layer');
+goog.require('ol.source.Image');
 
 
 
@@ -58,7 +59,8 @@ ol.renderer.dom.ImageLayer.prototype.renderFrame =
   var image = this.image_;
   var imageLayer = this.getLayer();
   goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
-  var imageSource = imageLayer.getImageSource();
+  var imageSource = imageLayer.getSource();
+  goog.asserts.assertInstanceof(imageSource, ol.source.Image);
 
   var hints = frameState.viewHints;
 
diff --git a/src/ol/renderer/webgl/webglimagelayerrenderer.js b/src/ol/renderer/webgl/webglimagelayerrenderer.js
index df16e686de..58cdddc483 100644
--- a/src/ol/renderer/webgl/webglimagelayerrenderer.js
+++ b/src/ol/renderer/webgl/webglimagelayerrenderer.js
@@ -12,6 +12,7 @@ goog.require('ol.ImageState');
 goog.require('ol.ViewHint');
 goog.require('ol.layer.Image');
 goog.require('ol.renderer.webgl.Layer');
+goog.require('ol.source.Image');
 
 
 
@@ -88,7 +89,8 @@ ol.renderer.webgl.ImageLayer.prototype.renderFrame =
   var texture = this.texture;
   var imageLayer = this.getLayer();
   goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
-  var imageSource = imageLayer.getImageSource();
+  var imageSource = imageLayer.getSource();
+  goog.asserts.assertInstanceof(imageSource, ol.source.Image);
 
   var hints = frameState.viewHints;