diff --git a/src/ol/source/Image.js b/src/ol/source/Image.js
index df934ad189..4f0f3c3f08 100644
--- a/src/ol/source/Image.js
+++ b/src/ol/source/Image.js
@@ -41,6 +41,32 @@ const ImageSourceEventType = {
 };
 
 
+/**
+ * @classdesc
+ * Events emitted by {@link ol.source.Image} instances are instances of this
+ * type.
+ *
+ * @constructor
+ * @extends {ol.events.Event}
+ * @implements {oli.source.ImageEvent}
+ * @param {string} type Type.
+ * @param {ol.Image} image The image.
+ */
+const ImageSourceEvent = function(type, image) {
+
+  Event.call(this, type);
+
+  /**
+   * The image related to the event.
+   * @type {ol.Image}
+   * @api
+   */
+  this.image = image;
+
+};
+inherits(ImageSourceEvent, Event);
+
+
 /**
  * @classdesc
  * Abstract base class; normally only used for creating subclasses and not
@@ -174,17 +200,17 @@ ImageSource.prototype.handleImageChange = function(event) {
   switch (image.getState()) {
     case ImageState.LOADING:
       this.dispatchEvent(
-        new ImageSource.Event(ImageSourceEventType.IMAGELOADSTART,
+        new ImageSourceEvent(ImageSourceEventType.IMAGELOADSTART,
           image));
       break;
     case ImageState.LOADED:
       this.dispatchEvent(
-        new ImageSource.Event(ImageSourceEventType.IMAGELOADEND,
+        new ImageSourceEvent(ImageSourceEventType.IMAGELOADEND,
           image));
       break;
     case ImageState.ERROR:
       this.dispatchEvent(
-        new ImageSource.Event(ImageSourceEventType.IMAGELOADERROR,
+        new ImageSourceEvent(ImageSourceEventType.IMAGELOADERROR,
           image));
       break;
     default:
@@ -199,35 +225,9 @@ ImageSource.prototype.handleImageChange = function(event) {
  * @param {ol.Image} image Image.
  * @param {string} src Source.
  */
-ImageSource.defaultImageLoadFunction = function(image, src) {
+export function defaultImageLoadFunction(image, src) {
   image.getImage().src = src;
-};
-
-
-/**
- * @classdesc
- * Events emitted by {@link ol.source.Image} instances are instances of this
- * type.
- *
- * @constructor
- * @extends {ol.events.Event}
- * @implements {oli.source.ImageEvent}
- * @param {string} type Type.
- * @param {ol.Image} image The image.
- */
-ImageSource.Event = function(type, image) {
-
-  Event.call(this, type);
-
-  /**
-   * The image related to the event.
-   * @type {ol.Image}
-   * @api
-   */
-  this.image = image;
-
-};
-inherits(ImageSource.Event, Event);
+}
 
 
 export default ImageSource;
diff --git a/src/ol/source/ImageArcGISRest.js b/src/ol/source/ImageArcGISRest.js
index 6a4b5e600d..c2461985b4 100644
--- a/src/ol/source/ImageArcGISRest.js
+++ b/src/ol/source/ImageArcGISRest.js
@@ -8,7 +8,7 @@ import {listen} from '../events.js';
 import EventType from '../events/EventType.js';
 import {containsExtent, getHeight, getWidth} from '../extent.js';
 import {assign} from '../obj.js';
-import ImageSource from '../source/Image.js';
+import ImageSource, {defaultImageLoadFunction} from '../source/Image.js';
 import {appendParams} from '../uri.js';
 
 /**
@@ -60,7 +60,7 @@ const ImageArcGISRest = function(opt_options) {
    * @type {ol.ImageLoadFunctionType}
    */
   this.imageLoadFunction_ = options.imageLoadFunction !== undefined ?
-    options.imageLoadFunction : ImageSource.defaultImageLoadFunction;
+    options.imageLoadFunction : defaultImageLoadFunction;
 
 
   /**
diff --git a/src/ol/source/ImageMapGuide.js b/src/ol/source/ImageMapGuide.js
index 1068840ac5..841004f5e5 100644
--- a/src/ol/source/ImageMapGuide.js
+++ b/src/ol/source/ImageMapGuide.js
@@ -7,7 +7,7 @@ import {listen} from '../events.js';
 import EventType from '../events/EventType.js';
 import {containsExtent, getCenter, getHeight, getWidth, scaleFromCenter} from '../extent.js';
 import {assign} from '../obj.js';
-import ImageSource from '../source/Image.js';
+import ImageSource, {defaultImageLoadFunction} from '../source/Image.js';
 import {appendParams} from '../uri.js';
 
 /**
@@ -58,7 +58,7 @@ const ImageMapGuide = function(options) {
    * @type {ol.ImageLoadFunctionType}
    */
   this.imageLoadFunction_ = options.imageLoadFunction !== undefined ?
-    options.imageLoadFunction : ImageSource.defaultImageLoadFunction;
+    options.imageLoadFunction : defaultImageLoadFunction;
 
   /**
    * @private
diff --git a/src/ol/source/ImageStatic.js b/src/ol/source/ImageStatic.js
index 0481f3109b..304b5ace52 100644
--- a/src/ol/source/ImageStatic.js
+++ b/src/ol/source/ImageStatic.js
@@ -9,7 +9,7 @@ import {listen} from '../events.js';
 import EventType from '../events/EventType.js';
 import {intersects, getHeight, getWidth} from '../extent.js';
 import {get as getProjection} from '../proj.js';
-import ImageSource from '../source/Image.js';
+import ImageSource, {defaultImageLoadFunction} from '../source/Image.js';
 
 /**
  * @classdesc
@@ -28,7 +28,7 @@ const Static = function(options) {
 
   const /** @type {ol.ImageLoadFunctionType} */ imageLoadFunction =
       options.imageLoadFunction !== undefined ?
-        options.imageLoadFunction : ImageSource.defaultImageLoadFunction;
+        options.imageLoadFunction : defaultImageLoadFunction;
 
   ImageSource.call(this, {
     attributions: options.attributions,
diff --git a/src/ol/source/ImageWMS.js b/src/ol/source/ImageWMS.js
index e78a7ebe22..f0d2c4a858 100644
--- a/src/ol/source/ImageWMS.js
+++ b/src/ol/source/ImageWMS.js
@@ -12,7 +12,7 @@ import {containsExtent, getCenter, getForViewAndSize, getHeight, getWidth} from
 import {assign} from '../obj.js';
 import {get as getProjection, transform} from '../proj.js';
 import {calculateSourceResolution} from '../reproj.js';
-import ImageSource from '../source/Image.js';
+import ImageSource, {defaultImageLoadFunction} from '../source/Image.js';
 import WMSServerType from '../source/WMSServerType.js';
 import {compareVersions} from '../string.js';
 import {appendParams} from '../uri.js';
@@ -55,7 +55,7 @@ const ImageWMS = function(opt_options) {
    * @type {ol.ImageLoadFunctionType}
    */
   this.imageLoadFunction_ = options.imageLoadFunction !== undefined ?
-    options.imageLoadFunction : ImageSource.defaultImageLoadFunction;
+    options.imageLoadFunction : defaultImageLoadFunction;
 
   /**
    * @private
diff --git a/test/spec/ol/imagetile.test.js b/test/spec/ol/imagetile.test.js
index fb897ecde2..eb35ed9f18 100644
--- a/test/spec/ol/imagetile.test.js
+++ b/test/spec/ol/imagetile.test.js
@@ -2,7 +2,7 @@ import ImageTile from '../../../src/ol/ImageTile.js';
 import TileState from '../../../src/ol/TileState.js';
 import {listen, unlistenByKey} from '../../../src/ol/events.js';
 import EventType from '../../../src/ol/events/EventType.js';
-import ImageSource from '../../../src/ol/source/Image.js';
+import {defaultImageLoadFunction} from '../../../src/ol/source/Image.js';
 
 
 describe('ol.ImageTile', function() {
@@ -13,7 +13,7 @@ describe('ol.ImageTile', function() {
       const tileCoord = [0, 0, 0];
       const state = TileState.IDLE;
       const src = 'spec/ol/data/osm-0-0-0.png';
-      const tileLoadFunction = ImageSource.defaultImageLoadFunction;
+      const tileLoadFunction = defaultImageLoadFunction;
       const tile = new ImageTile(tileCoord, state, src, null, tileLoadFunction);
 
       let previousState = tile.getState();
@@ -38,7 +38,7 @@ describe('ol.ImageTile', function() {
       const tileCoord = [0, 0, 0];
       const state = TileState.ERROR;
       const src = 'spec/ol/data/osm-0-0-0.png';
-      const tileLoadFunction = ImageSource.defaultImageLoadFunction;
+      const tileLoadFunction = defaultImageLoadFunction;
       const tile = new ImageTile(tileCoord, state, src, null, tileLoadFunction);
 
       let previousState = tile.getState();
@@ -63,7 +63,7 @@ describe('ol.ImageTile', function() {
       const tileCoord = [0, 0, 0];
       const state = TileState.IDLE;
       const src = 'spec/ol/data/osm-0-0-99.png';
-      const tileLoadFunction = ImageSource.defaultImageLoadFunction;
+      const tileLoadFunction = defaultImageLoadFunction;
       const tile = new ImageTile(tileCoord, state, src, null, tileLoadFunction);
 
       const key = listen(tile, EventType.CHANGE, function(event) {
@@ -89,7 +89,7 @@ describe('ol.ImageTile', function() {
       const tileCoord = [0, 0, 0];
       const state = TileState.IDLE;
       const src = 'spec/ol/data/osm-0-0-0.png';
-      const tileLoadFunction = ImageSource.defaultImageLoadFunction;
+      const tileLoadFunction = defaultImageLoadFunction;
       const tile = new ImageTile(tileCoord, state, src, null, tileLoadFunction);
       tile.load();
       expect(tile.getState()).to.be(TileState.LOADING);
diff --git a/test/spec/ol/tilequeue.test.js b/test/spec/ol/tilequeue.test.js
index 865e78a602..c92e02a34a 100644
--- a/test/spec/ol/tilequeue.test.js
+++ b/test/spec/ol/tilequeue.test.js
@@ -2,7 +2,7 @@ import ImageTile from '../../../src/ol/ImageTile.js';
 import Tile from '../../../src/ol/Tile.js';
 import TileQueue from '../../../src/ol/TileQueue.js';
 import TileState from '../../../src/ol/TileState.js';
-import ImageSource from '../../../src/ol/source/Image.js';
+import {defaultImageLoadFunction} from '../../../src/ol/source/Image.js';
 import {DROP} from '../../../src/ol/structs/PriorityQueue.js';
 
 
@@ -32,7 +32,7 @@ describe('ol.TileQueue', function() {
         'yH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==';
 
     const tileLoadFunction = opt_tileLoadFunction ?
-      opt_tileLoadFunction : ImageSource.defaultImageLoadFunction;
+      opt_tileLoadFunction : defaultImageLoadFunction;
     return new ImageTile(tileCoord, state, src, null, tileLoadFunction);
   }