--- a/browser/base/content/aboutDialog-appUpdater.js
+++ b/browser/base/content/aboutDialog-appUpdater.js
@@ -23,19 +23,22 @@ function onUnload(aEvent) {
   gAppUpdater = null;
 }
 
 
 function appUpdater()
 {
   this.updateDeck = document.getElementById("updateDeck");
 
-  // Hide the update deck when there is already an update window open to avoid
-  // syncing issues between them.
-  if (Services.wm.getMostRecentWindow("Update:Wizard")) {
+  // Hide the update deck when the update window is already open and it's not
+  // already applied, to avoid syncing issues between them. Applied updates
+  // don't have any information to sync between the windows as they both just
+  // show the "Restart to continue"-type button.
+  if (Services.wm.getMostRecentWindow("Update:Wizard") &&
+      !this.isApplied) {
     this.updateDeck.hidden = true;
     return;
   }
 
   XPCOMUtils.defineLazyServiceGetter(this, "aus",
                                      "@mozilla.org/updates/update-service;1",
                                      "nsIApplicationUpdateService");
   XPCOMUtils.defineLazyServiceGetter(this, "checker",