diff --git a/js/ui/workspaceThumbnail.js b/js/ui/workspaceThumbnail.js
index 7d5d2c08c..5565a1e41 100644
--- a/js/ui/workspaceThumbnail.js
+++ b/js/ui/workspaceThumbnail.js
@@ -1159,7 +1159,7 @@ var ThumbnailsBox = new Lang.Class({
     // The "porthole" is the portion of the screen that we show in the
     // workspaces
     _ensurePorthole() {
-        if (!Main.layoutManager.primaryMonitor)
+        if (!Main.layoutManager.primaryMonitor || !Main.overview.visible)
             return false;
 
         if (!this._porthole)