diff --git a/lib/assets/javascripts/unobtrusive_flash.js b/lib/assets/javascripts/unobtrusive_flash.js
index d33be29..8e56a8d 100644
--- a/lib/assets/javascripts/unobtrusive_flash.js
+++ b/lib/assets/javascripts/unobtrusive_flash.js
@@ -6,6 +6,7 @@ $(function() {
       yesterday.setDate(yesterday.getDate() - 1);
       var hostParts = window.location.host.split('.').reverse();
       var expireHost = hostParts.shift();
+      expireHost = expireHost.replace(/^([a-z]{1,})\:[0-9]{1,5}/, '$1');
       $.each(hostParts, function(i,part) {
         expireHost = part + '.' + expireHost;
         document.cookie = cookieName+'=; path=/;expires='+yesterday+'; domain='+expireHost;