diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index 9a56bd7c2..7d22a425b 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -480,7 +480,7 @@ const Notification = new Lang.Class({
         this.forFeedback = false;
         this.expanded = false;
         this.focused = false;
-        this.acknowledged = false;
+        this._acknowledged = false;
         this._destroyed = false;
         this._customContent = false;
         this.bannerBodyText = null;
@@ -822,6 +822,17 @@ const Notification = new Lang.Class({
         return this.addButton(button, callback);
     },
 
+    get acknowledged() {
+        return this._acknowledged;
+    },
+
+    set acknowledged(v) {
+        if (this._acknowledged == v)
+            return;
+        this._acknowledged = v;
+        this.emit('acknowledged-changed');
+    },
+
     setUrgency: function(urgency) {
         this.urgency = urgency;
     },
@@ -1292,6 +1303,7 @@ const Source = new Lang.Class({
             return;
 
         notification.connect('destroy', Lang.bind(this, this._onNotificationDestroy));
+        notification.connect('acknowledged-changed', Lang.bind(this, this.countUpdated));
         this.notifications.push(notification);
         this.emit('notification-added', notification);