diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index f3ea1b5a0..6bbd6448f 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -550,13 +550,12 @@ Notification.prototype = {
 };
 Signals.addSignalMethods(Notification.prototype);
 
-function Source(id, title, createIcon) {
-    this._init(id, title, createIcon);
+function Source(title, createIcon) {
+    this._init(title, createIcon);
 }
 
 Source.prototype = {
-    _init: function(id, title, createIcon) {
-        this.id = id;
+    _init: function(title, createIcon) {
         this.title = title;
         if (createIcon)
             this.createIcon = createIcon;
@@ -809,7 +808,7 @@ MessageTray.prototype = {
                     this._updateState();
             }));
 
-        this._summaryItems = {};
+        this._summaryItems = [];
         this._longestSummaryItem = null;
     },
 
@@ -827,12 +826,20 @@ MessageTray.prototype = {
     },
 
     contains: function(source) {
-        return this._summaryItems.hasOwnProperty(source.id);
+        return this._getIndexOfSummaryItemForSource(source) >= 0;
+    },
+
+    _getIndexOfSummaryItemForSource: function(source) {
+        for (let i = 0; i < this._summaryItems.length; i++) {
+            if (this._summaryItems[i].source == source)
+                return i;
+        }
+        return -1;
     },
 
     add: function(source) {
         if (this.contains(source)) {
-            log('Trying to re-add source ' + source.id);
+            log('Trying to re-add source ' + source.title);
             return;
         }
 
@@ -844,14 +851,14 @@ MessageTray.prototype = {
 
         let newItemTitleWidth = summaryItem.getTitleNaturalWidth();
         if (newItemTitleWidth > minTitleWidth) {
-            for (sourceId in this._summaryItems) {
-                this._summaryItems[sourceId].setMinTitleWidth(newItemTitleWidth);
+            for (let i = 0; i < this._summaryItems.length; i++) {
+                this._summaryItems[i].setMinTitleWidth(newItemTitleWidth);
             }
             summaryItem.setMinTitleWidth(newItemTitleWidth);
             this._longestSummaryItem = summaryItem;
         }
 
-        this._summaryItems[source.id] = summaryItem;
+        this._summaryItems.push(summaryItem);
 
         source.connect('notify', Lang.bind(this, this._onNotify));
 
@@ -872,7 +879,8 @@ MessageTray.prototype = {
     },
 
     removeSource: function(source) {
-        if (!this.contains(source))
+        let index = this._getIndexOfSummaryItemForSource(source);
+        if (index == -1)
             return;
 
         // remove all notifications with this source from the queue
@@ -883,26 +891,26 @@ MessageTray.prototype = {
         }
         this._notificationQueue = newNotificationQueue;
 
-        this._summary.remove_actor(this._summaryItems[source.id].actor);
+        this._summary.remove_actor(this._summaryItems[index].actor);
         if (this._summary.get_children().length > 0)
             this._summaryNeedsToBeShown = true;
         else
             this._summaryNeedsToBeShown = false;
 
-        delete this._summaryItems[source.id];
+        this._summaryItems.splice(index, 1);
         if (this._longestSummaryItem.source == source) {
 
             let maxTitleWidth = 0;
             this._longestSummaryItem = null;
-            for (sourceId in this._summaryItems) {
-                let summaryItem = this._summaryItems[sourceId];
+            for (let i = 0; i < this._summaryItems.length; i++) {
+                let summaryItem = this._summaryItems[i];
                 if (summaryItem.getTitleNaturalWidth() > maxTitleWidth) {
                     maxTitleWidth = summaryItem.getTitleNaturalWidth();
                     this._longestSummaryItem = summaryItem;
                 }
             }
-            for (sourceId in this._summaryItems) {
-                this._summaryItems[sourceId].setMinTitleWidth(maxTitleWidth);
+            for (let i = 0; i < this._summaryItems.length; i++) {
+                this._summaryItems[i].setMinTitleWidth(maxTitleWidth);
             }
         }
 
@@ -925,12 +933,6 @@ MessageTray.prototype = {
             this._updateState();
     },
 
-    removeSourceByApp: function(app) {
-        for (let sourceId in this._summaryItems)
-            if (this._summaryItems[sourceId].source.app == app)
-                this.removeSource(this._summaryItems[sourceId].source);
-    },
-
     removeNotification: function(notification) {
         if (this._notification == notification && (this._notificationState == State.SHOWN || this._notificationState == State.SHOWING)) {
             if (this._notificationTimeoutId) {
@@ -947,12 +949,6 @@ MessageTray.prototype = {
             this._notificationQueue.splice(index, 1);
     },
 
-    getSource: function(id) {
-        if (this._summaryItems[id])
-            return this._summaryItems[id].source;
-        return null;
-    },
-
     _getNotification: function(id, source) {
         if (this._notification && this._notification.id == id)
             return this._notification;
diff --git a/js/ui/notificationDaemon.js b/js/ui/notificationDaemon.js
index a6a55c5bf..4e7802281 100644
--- a/js/ui/notificationDaemon.js
+++ b/js/ui/notificationDaemon.js
@@ -107,6 +107,7 @@ NotificationDaemon.prototype = {
                                   Lang.bind(this, this._acquiredName),
                                   Lang.bind(this, this._lostName));
 
+        this._sources = {};
         this._currentNotifications = {};
 
         Shell.WindowTracker.get_default().connect('notify::focus-app',
@@ -140,13 +141,9 @@ NotificationDaemon.prototype = {
         }
     },
 
-    _sourceId: function(id) {
-        return 'source-' + id;
-    },
-
     Notify: function(appName, replacesId, icon, summary, body,
                      actions, hints, timeout) {
-        let source = Main.messageTray.getSource(this._sourceId(appName));
+        let source = this._sources[appName];
         let id = null;
 
         // Filter out notifications from Empathy, since we
@@ -167,13 +164,18 @@ NotificationDaemon.prototype = {
         // been acknowledged.
         if (source == null) {
             let title = appNameMap[appName] || appName;
-            source = new Source(this._sourceId(appName), title, icon, hints);
+            source = new Source(title, icon, hints);
             Main.messageTray.add(source);
+            this._sources[appName] = source;
 
             source.connect('clicked', Lang.bind(this,
                 function() {
                     source.destroy();
                 }));
+            source.connect('destroy', Lang.bind(this,
+                function() {
+                    delete this._sources[appName];
+                }));
 
             let sender = DBus.getCurrentMessageContext().sender;
             let busProxy = new Bus();
@@ -265,8 +267,16 @@ NotificationDaemon.prototype = {
 
     _onFocusAppChanged: function() {
         let tracker = Shell.WindowTracker.get_default();
-        if (tracker.focus_app)
-            Main.messageTray.removeSourceByApp(tracker.focus_app);
+        if (!tracker.focus_app)
+            return;
+
+        for (let id in this._sources) {
+            let source = this._sources[id];
+            if (source.app == tracker.focus_app) {
+                source.destroy();
+                return;
+            }
+        }
     },
 
     _actionInvoked: function(notification, action, source, id) {
@@ -291,15 +301,15 @@ NotificationDaemon.prototype = {
 
 DBus.conformExport(NotificationDaemon.prototype, NotificationDaemonIface);
 
-function Source(sourceId, title, icon, hints) {
-    this._init(sourceId, title, icon, hints);
+function Source(title, icon, hints) {
+    this._init(title, icon, hints);
 }
 
 Source.prototype = {
     __proto__:  MessageTray.Source.prototype,
 
-    _init: function(sourceId, title, icon, hints) {
-        MessageTray.Source.prototype._init.call(this, sourceId, title);
+    _init: function(title, icon, hints) {
+        MessageTray.Source.prototype._init.call(this, title);
 
         this.app = null;
         this._openAppRequested = false;
diff --git a/js/ui/telepathyClient.js b/js/ui/telepathyClient.js
index e23f4fa1a..722dffc48 100644
--- a/js/ui/telepathyClient.js
+++ b/js/ui/telepathyClient.js
@@ -445,7 +445,7 @@ Source.prototype = {
     __proto__:  MessageTray.Source.prototype,
 
     _init: function(accountPath, connPath, channelPath, targetHandle, targetHandleType, targetId) {
-        MessageTray.Source.prototype._init.call(this, targetId, targetId);
+        MessageTray.Source.prototype._init.call(this, targetId);
 
         this._accountPath = accountPath;
 
diff --git a/js/ui/windowAttentionHandler.js b/js/ui/windowAttentionHandler.js
index ceba3f9ef..fa8aefaad 100644
--- a/js/ui/windowAttentionHandler.js
+++ b/js/ui/windowAttentionHandler.js
@@ -14,10 +14,12 @@ function WindowAttentionHandler() {
 
 WindowAttentionHandler.prototype = {
     _init : function() {
+        this._startupIds = {};
+        this._sources = {};
+
         let display = global.screen.get_display();
         display.connect('window-demands-attention', Lang.bind(this, this._onWindowDemandsAttention));
         let tracker = Shell.WindowTracker.get_default();
-        this._startupIds = {};
         tracker.connect('startup-sequence-changed', Lang.bind(this, this._onStartupSequenceChanged));
     },
 
@@ -29,10 +31,6 @@ WindowAttentionHandler.prototype = {
         }
     },
 
-    _sourceId : function(appId) {
-        return 'attention-' + appId;
-    },
-
     _getTitle : function(app, window) {
         if (this._startupIds[window.get_startup_id()])
             return app.get_name();
@@ -61,12 +59,15 @@ WindowAttentionHandler.prototype = {
 
         let tracker = Shell.WindowTracker.get_default();
         let app = tracker.get_window_app(window);
+        let appId = app.get_id();
 
-        let source = Main.messageTray.getSource(this._sourceId(app.get_id()));
+        let source = this._sources[appId];
         if (source == null) {
-            source = new Source(this._sourceId(app.get_id()), app, window);
+            source = new Source(app, window);
+            this._sources[appId] = source;
             Main.messageTray.add(source);
             source.connect('clicked', Lang.bind(this, function() { source.destroy(); }));
+            source.connect('destroy', Lang.bind(this, function() { delete this._sources[appId]; }));
         }
 
         let notification = new MessageTray.Notification(window.get_startup_id(), source, this._getTitle(app, window), this._getBanner(app, window), true);
@@ -82,15 +83,15 @@ WindowAttentionHandler.prototype = {
     }
 };
 
-function Source(sourceId, app, window) {
-    this._init(sourceId, app, window);
+function Source(app, window) {
+    this._init(app, window);
 }
 
 Source.prototype = {
     __proto__ : MessageTray.Source.prototype,
 
-    _init: function(sourceId, app, window) {
-        MessageTray.Source.prototype._init.call(this, sourceId, app.get_name());
+    _init: function(app, window) {
+        MessageTray.Source.prototype._init.call(this, app.get_name());
         this._window = window;
         this._app = app;
     },