Index: wp-admin/js/widgets.js
===================================================================
--- wp-admin/js/widgets.js	(revision 26929)
+++ wp-admin/js/widgets.js	(working copy)
@@ -50,10 +50,13 @@
 						css[ margin ] = widgetWidth - ( targetWidth + 30 ) + 'px';
 						widget.css( css );
 					}
+					widget.addClass( 'widget-open' );
 					inside.slideDown('fast');
+
 				} else {
-					inside.slideUp('fast', function() {
+						inside.slideUp('fast', function() {
 						widget.attr( 'style', '' );
+						widget.removeClass( 'widget-open' );
 					});
 				}
 				e.preventDefault();
Index: wp-admin/css/wp-admin.css
===================================================================
--- wp-admin/css/wp-admin.css	(revision 26929)
+++ wp-admin/css/wp-admin.css	(working copy)
@@ -11090,6 +11090,10 @@
 	text-decoration: none !important;
 }
 
+.widget-open .widget-top a.widget-action:after {
+	content: '\f142';
+}
+
 .widget-top a.widget-action:after {
 	padding: 12px 12px 0;
 }