diff --git a/src/ol/renderer/canvas/canvasimagelayerrenderer.js b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
index 7f5f477058..da68e20e4b 100644
--- a/src/ol/renderer/canvas/canvasimagelayerrenderer.js
+++ b/src/ol/renderer/canvas/canvasimagelayerrenderer.js
@@ -1,5 +1,6 @@
 goog.provide('ol.renderer.canvas.ImageLayer');
 
+goog.require('goog.asserts');
 goog.require('goog.events');
 goog.require('goog.events.EventType');
 goog.require('goog.vec.Mat4');
@@ -47,15 +48,6 @@ ol.renderer.canvas.ImageLayer.prototype.getImage = function() {
 };
 
 
-/**
- * @protected
- * @return {ol.layer.Image} Single image layer.
- */
-ol.renderer.canvas.ImageLayer.prototype.getImageLayer = function() {
-  return /** @type {ol.layer.Image} */ (this.getLayer());
-};
-
-
 /**
  * @inheritDoc
  */
@@ -76,7 +68,8 @@ ol.renderer.canvas.ImageLayer.prototype.renderFrame =
   var viewRotation = view2DState.rotation;
 
   var image;
-  var imageLayer = this.getImageLayer();
+  var imageLayer = this.getLayer();
+  goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
   var imageSource = imageLayer.getImageSource();
 
   var hints = frameState.viewHints;
diff --git a/src/ol/renderer/dom/domimagelayerrenderer.js b/src/ol/renderer/dom/domimagelayerrenderer.js
index b5f9971fab..cc5843b453 100644
--- a/src/ol/renderer/dom/domimagelayerrenderer.js
+++ b/src/ol/renderer/dom/domimagelayerrenderer.js
@@ -1,5 +1,6 @@
 goog.provide('ol.renderer.dom.ImageLayer');
 
+goog.require('goog.asserts');
 goog.require('goog.dom');
 goog.require('goog.dom.TagName');
 goog.require('goog.events');
@@ -43,15 +44,6 @@ ol.renderer.dom.ImageLayer = function(mapRenderer, imageLayer) {
 goog.inherits(ol.renderer.dom.ImageLayer, ol.renderer.dom.Layer);
 
 
-/**
- * @protected
- * @return {ol.layer.Image} Image layer.
- */
-ol.renderer.dom.ImageLayer.prototype.getImageLayer = function() {
-  return /** @type {ol.layer.Image} */ (this.getLayer());
-};
-
-
 /**
  * @inheritDoc
  */
@@ -64,7 +56,8 @@ ol.renderer.dom.ImageLayer.prototype.renderFrame =
   var viewRotation = view2DState.rotation;
 
   var image = this.image_;
-  var imageLayer = this.getImageLayer();
+  var imageLayer = this.getLayer();
+  goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
   var imageSource = imageLayer.getImageSource();
 
   var hints = frameState.viewHints;
diff --git a/src/ol/renderer/webgl/webglimagelayerrenderer.js b/src/ol/renderer/webgl/webglimagelayerrenderer.js
index 0249e1c336..df16e686de 100644
--- a/src/ol/renderer/webgl/webglimagelayerrenderer.js
+++ b/src/ol/renderer/webgl/webglimagelayerrenderer.js
@@ -71,15 +71,6 @@ ol.renderer.webgl.ImageLayer.prototype.createTexture_ = function(image) {
 };
 
 
-/**
- * @protected
- * @return {ol.layer.Image} Tile layer.
- */
-ol.renderer.webgl.ImageLayer.prototype.getImageLayer = function() {
-  return /** @type {ol.layer.Image} */ (this.getLayer());
-};
-
-
 /**
  * @inheritDoc
  */
@@ -95,7 +86,8 @@ ol.renderer.webgl.ImageLayer.prototype.renderFrame =
 
   var image = this.image_;
   var texture = this.texture;
-  var imageLayer = this.getImageLayer();
+  var imageLayer = this.getLayer();
+  goog.asserts.assertInstanceof(imageLayer, ol.layer.Image);
   var imageSource = imageLayer.getImageSource();
 
   var hints = frameState.viewHints;