Index: src/wp-admin/js/widgets.js
===================================================================
--- src/wp-admin/js/widgets.js	(revision 33777)
+++ src/wp-admin/js/widgets.js	(working copy)
@@ -178,6 +178,7 @@
 					inside = ui.item.children('.widget-inside');
 
 				if ( inside.css('display') === 'block' ) {
+					ui.item.removeClass('open');
 					inside.hide();
 					$(this).sortable('refreshPositions');
 				}