diff --git a/src/iiiftilesource.js b/src/iiiftilesource.js
index 200767c8..d1331cd3 100644
--- a/src/iiiftilesource.js
+++ b/src/iiiftilesource.js
@@ -150,7 +150,7 @@ $.extend( $.IIIFTileSource.prototype, $.TileSource.prototype, /** @lends OpenSea
      * this tile source.
      * @function
      * @param {Object|Array} data
-     * @param {String} optional - url
+     * @param {String} [url] - url
      */
 
     supports: function( data, url ) {
@@ -249,13 +249,6 @@ $.extend( $.IIIFTileSource.prototype, $.TileSource.prototype, /** @lends OpenSea
                 }
             }
 
-            // normalize the various possible id properties to an internal one
-            data._id = data["@id"] || data["id"] || data['identifier'] || null;
-
-            if (!data._id) {
-                throw new Error( 'Could not determine a property for the tile source ID.' );
-            }
-
             if (data.preferredFormats) {
                 for (var f = 0; f < data.preferredFormats.length; f++ ) {
                     if ( OpenSeadragon.imageFormatSupported(data.preferredFormats[f]) ) {