diff --git a/js/ui/workspace.js b/js/ui/workspace.js
index 5aa9ba66ca7768eec23731aad0a791614b9f2da6..f09f487142b9da3dc128e8d00358b5832d4340d5 100644
--- a/js/ui/workspace.js
+++ b/js/ui/workspace.js
@@ -110,6 +110,7 @@ var WindowClone = new Lang.Class({
         this.metaWindow = realWindow.meta_window;
         this.metaWindow._delegate = this;
         this._workspace = workspace;
+        this._attachedDialogs = [];
 
         this._windowClone = new Clutter.Clone({ source: realWindow });
         // We expect this.actor to be used for all interaction rather than
@@ -208,6 +209,12 @@ var WindowClone = new Lang.Class({
     },
 
     addDialog(win) {
+        let realWin = win.get_compositor_private();
+        if (this._attachedDialogs.includes(realWin))
+            return;
+
+        this._attachedDialogs.push(realWin);
+
         let parent = win.get_transient_for();
         while (parent.is_attached_dialog())
             parent = parent.get_transient_for();
@@ -225,7 +232,7 @@ var WindowClone = new Lang.Class({
     },
 
     hasAttachedDialogs() {
-        return this.actor.get_n_children() > 1;
+        return this._attachedDialogs.length > 1;
     },
 
     _doAddAttachedDialog(metaWin, realWin) {
@@ -235,6 +242,9 @@ var WindowClone = new Lang.Class({
         clone._posChangedId = metaWin.connect('position-changed',
             this._onMetaWindowSizeChanged.bind(this));
         clone._destroyId = realWin.connect('destroy', () => {
+            let idx = this._attachedDialogs.indexOf(realWin);
+            this._attachedDialogs.splice(idx, 1);
+
             clone.destroy();
 
             this._onMetaWindowSizeChanged();
diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index cf21e13170adf93752150428e6e44bc710bef53b..b648821479873a9c53490dba736864e0fafa1ea4 100644
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -151,7 +151,7 @@ var WindowClone = new Lang.Class({
 
     _doAddAttachedDialog(metaDialog, realDialog) {
         let clone = new Clutter.Clone({ source: realDialog });
-        this._updateDialogPosition(realDialog, clone);
+        this._updateDialogPosition(metaDialog, clone);
 
         clone._updateId = realDialog.connect('notify::position', dialog => {
             this._updateDialogPosition(dialog, clone);
@@ -162,8 +162,7 @@ var WindowClone = new Lang.Class({
         this.actor.add_child(clone);
     },
 
-    _updateDialogPosition(realDialog, cloneDialog) {
-        let metaDialog = realDialog.meta_window;
+    _updateDialogPosition(metaDialog, cloneDialog) {
         let dialogRect = metaDialog.get_frame_rect();
         let rect = this.metaWindow.get_frame_rect();