diff --git a/src/imagetilesource.js b/src/imagetilesource.js
index 0bf26844..417243c6 100644
--- a/src/imagetilesource.js
+++ b/src/imagetilesource.js
@@ -50,7 +50,6 @@
      * @extends OpenSeadragon.TileSource
      * @param {Object} options Options object.
      * @param {String} options.url URL of the image
-     * @param {String} options.referenceStripThumbnailUrl URL of the dedicated thumbnail image
      * @param {Boolean} [options.buildPyramid=true] If set to true (default), a
      * pyramid will be built internally to provide a better downsampling.
      * @param {String|Boolean} [options.crossOriginPolicy=false] Valid values are
diff --git a/src/tilesource.js b/src/tilesource.js
index e83c4fab..bb3e433e 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -60,6 +60,8 @@
  *      the extending classes implementation of 'configure'.
  * @param {String} [options.url]
  *      The URL for the data necessary for this TileSource.
+ * @param {String} [options.referenceStripThumbnailUrl]
+ *      The URL for the thumbnail image to be used by the reference strip
  * @param {Function} [options.success]
  *      A function to be called upon successful creation.
  * @param {Boolean} [options.ajaxWithCredentials]