Index: /CKEditor/branches/features/aria/_source/plugins/dialogui/plugin.js
===================================================================
--- /CKEditor/branches/features/aria/_source/plugins/dialogui/plugin.js	(revision 4984)
+++ /CKEditor/branches/features/aria/_source/plugins/dialogui/plugin.js	(revision 4985)
@@ -832,4 +832,5 @@
 				};
 
+				this._ = { children : childObjList };
 				CKEDITOR.ui.dialog.uiElement.call( this, dialog, elementDefinition, htmlList, 'fieldset', null, null, innerHTML );
 			}
@@ -1388,5 +1389,5 @@
 	CKEDITOR.ui.dialog.fileButton.prototype = new CKEDITOR.ui.dialog.button;
 
-	CKEDITOR.ui.dialog.fieldset.prototype = CKEDITOR.ui.dialog.uiElement.prototype;
+	CKEDITOR.ui.dialog.fieldset.prototype = CKEDITOR.tools.extend( {}, CKEDITOR.ui.dialog.hbox.prototype );
 
 	CKEDITOR.dialog.addUIElement( 'text', textBuilder );