diff --git a/lib/yui/chooserdialogue/chooserdialogue.js b/lib/yui/chooserdialogue/chooserdialogue.js
index 1c877b81056..496084707c9 100644
--- a/lib/yui/chooserdialogue/chooserdialogue.js
+++ b/lib/yui/chooserdialogue/chooserdialogue.js
@@ -43,8 +43,7 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
                 draggable : true,
                 visible : false, // Hide by default
                 zindex : 100, // Display in front of other items
-                lightbox : true, // This dialogue should be modal
-                shim : true
+                lightbox : true // This dialogue should be modal
             };
 
             // Override with additional options