diff --git a/externs/olx.js b/externs/olx.js
index 16bddc6b9b..f1762651a0 100644
--- a/externs/olx.js
+++ b/externs/olx.js
@@ -903,105 +903,6 @@ olx.source.OSMOptions.prototype.url;
 olx.source.OSMOptions.prototype.wrapX;
 
 
-/**
- * @typedef {{attributions: (ol.AttributionLike|undefined),
- *     crossOrigin: (null|string|undefined),
- *     hidpi: (boolean|undefined),
- *     imageLoadFunction: (ol.ImageLoadFunctionType|undefined),
- *     params: Object.<string,*>,
- *     projection: ol.ProjectionLike,
- *     ratio: (number|undefined),
- *     resolutions: (Array.<number>|undefined),
- *     url: (string|undefined)}}
- */
-olx.source.ImageArcGISRestOptions;
-
-
-/**
- * Attributions.
- * @type {ol.AttributionLike|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.attributions;
-
-
-/**
- * The `crossOrigin` attribute for loaded images.  Note that you must provide a
- * `crossOrigin` value if you are using the WebGL renderer or if you want to
- * access pixel data with the Canvas renderer.  See
- * {@link https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image}
- * for more detail.
- * @type {null|string|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.crossOrigin;
-
-
-/**
- * Use the `ol.Map#pixelRatio` value when requesting the image from the remote
- * server. Default is `true`.
- * @type {boolean|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.hidpi;
-
-
-/**
- * Optional function to load an image given a URL.
- * @type {ol.ImageLoadFunctionType|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.imageLoadFunction;
-
-
-/**
- * ArcGIS Rest parameters. This field is optional. Service defaults will be
- * used for any fields not specified. `FORMAT` is `PNG32` by default. `F` is `IMAGE` by
- * default. `TRANSPARENT` is `true` by default.  `BBOX, `SIZE`, `BBOXSR`,
- * and `IMAGESR` will be set dynamically. Set `LAYERS` to
- * override the default service layer visibility. See
- * {@link http://resources.arcgis.com/en/help/arcgis-rest-api/index.html#/Export_Map/02r3000000v7000000/}
- * for further reference.
- * @type {Object.<string,*>|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.params;
-
-
-/**
- * Projection.
- * @type {ol.ProjectionLike}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.projection;
-
-
-/**
- * Ratio. `1` means image requests are the size of the map viewport, `2` means
- * twice the size of the map viewport, and so on. Default is `1.5`.
- * @type {number|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.ratio;
-
-
-/**
- * Resolutions. If specified, requests will be made for these resolutions only.
- * @type {Array.<number>|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.resolutions;
-
-
-/**
- * ArcGIS Rest service URL for a Map Service or Image Service. The
- * url should include /MapServer or /ImageServer.
- * @type {string|undefined}
- * @api
- */
-olx.source.ImageArcGISRestOptions.prototype.url;
-
-
 /**
  * @typedef {{attributions: (ol.AttributionLike|undefined),
  *     canvasFunction: ol.CanvasFunctionType,
diff --git a/src/ol/source/ImageArcGISRest.js b/src/ol/source/ImageArcGISRest.js
index 812d1607ae..4747f4f332 100644
--- a/src/ol/source/ImageArcGISRest.js
+++ b/src/ol/source/ImageArcGISRest.js
@@ -11,6 +11,34 @@ import {assign} from '../obj.js';
 import ImageSource, {defaultImageLoadFunction} from '../source/Image.js';
 import {appendParams} from '../uri.js';
 
+
+/**
+ * @typedef {Object} Options
+ * @property {ol.AttributionLike} [attributions] Attributions.
+ * @property {null|string} [crossOrigin] The `crossOrigin` attribute for loaded images.  Note that
+ * you must provide a `crossOrigin` value if you are using the WebGL renderer or if you want to
+ * access pixel data with the Canvas renderer.  See
+ * {@link https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_enabled_image} for more detail.
+ * @property {boolean} [hidpi=true] Use the `ol.Map#pixelRatio` value when requesting the image from
+ * the remote server.
+ * @property {ol.ImageLoadFunctionType} [imageLoadFunction] Optional function to load an image given
+ * a URL.
+ * @property {Object.<string,*>} params ArcGIS Rest parameters. This field is optional. Service
+ * defaults will be used for any fields not specified. `FORMAT` is `PNG32` by default. `F` is
+ * `IMAGE` by default. `TRANSPARENT` is `true` by default.  `BBOX, `SIZE`, `BBOXSR`, and `IMAGESR`
+ * will be set dynamically. Set `LAYERS` to override the default service layer visibility. See
+ * {@link http://resources.arcgis.com/en/help/arcgis-rest-api/index.html#/Export_Map/02r3000000v7000000/}
+ * for further reference.
+ * @property {module:ol/proj~ProjectionLike} projection Projection.
+ * @property {number} [ratio=1.5] Ratio. `1` means image requests are the size of the map viewport,
+ * `2` means twice the size of the map viewport, and so on.
+ * @property {Array.<number>} [resolutions] Resolutions. If specified, requests will be made for
+ * these resolutions only.
+ * @property {string} [url] ArcGIS Rest service URL for a Map Service or Image Service. The url
+ * should include /MapServer or /ImageServer.
+ */
+
+
 /**
  * @classdesc
  * Source for data from ArcGIS Rest services providing single, untiled images.
@@ -23,7 +51,7 @@ import {appendParams} from '../uri.js';
  * @constructor
  * @fires ol.source.Image.Event
  * @extends {ol.source.Image}
- * @param {olx.source.ImageArcGISRestOptions=} opt_options Image ArcGIS Rest Options.
+ * @param {module:ol/source/ImageArcGISRest~Options=} opt_options Image ArcGIS Rest Options.
  * @api
  */
 const ImageArcGISRest = function(opt_options) {