diff --git a/web/compatibility.js b/web/compatibility.js
index e9b69ed07..0d12c64a9 100644
--- a/web/compatibility.js
+++ b/web/compatibility.js
@@ -92,6 +92,13 @@ if (typeof PDFJS === 'undefined') {
   window.Float64Array = TypedArray;
 })();
 
+// URL = URL || webkitURL
+(function normalizeURLObject() {
+  if (!window.URL && window.webkitURL) {
+    window.URL = window.webkitURL;
+  }
+})();
+
 // Object.create() ?
 (function checkObjectCreateCompatibility() {
   if (typeof Object.create !== 'undefined')
diff --git a/web/viewer.js b/web/viewer.js
index 106164e19..d28afcc00 100644
--- a/web/viewer.js
+++ b/web/viewer.js
@@ -14,6 +14,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/* globals URL*/
 /* globals PDFJS, PDFBug, FirefoxCom, Stats, Cache, PDFFindBar */
 /* globals PDFFindController, ProgressBar, getFileName, CustomStyle */
 /* globals getOutputScale, TextLayerBuilder */
@@ -975,8 +976,7 @@ var PDFView = {
 //      );
 //  }
 //#endif
-    var URL = window.URL || window.webkitURL;
-    // If the PDF is not ready yet, or if createObjectURL is not supported,
+    // If the PDF is not ready yet, or if URL.createObjectURL is not supported,
     // just try to download with the url.
     if (!this.pdfDocument || !URL) {
         noData();