diff --git a/base/shared/annotation.js b/base/shared/annotation.js
index f7a23a6d..01830797 100755
--- a/base/shared/annotation.js
+++ b/base/shared/annotation.js
@@ -667,7 +667,7 @@ var LinkAnnotation = (function LinkAnnotationClosure() {
 
   // Lets URLs beginning with 'www.' default to using the 'http://' protocol.
   function addDefaultProtocolToUrl(url) {
-    if (url.indexOf('www.') === 0) {
+    if (url && url.indexOf('www.') === 0) {
       return ('http://' + url);
     }
     return url;