Index: src/wp-includes/post.php
===================================================================
--- src/wp-includes/post.php	(revision 35788)
+++ src/wp-includes/post.php	(working copy)
@@ -2409,6 +2409,15 @@
 		$wpdb->update( $wpdb->posts, $parent_data, $parent_where + array( 'post_type' => $post->post_type ) );
 	}
 
+	if ( $post->post_type == 'nav_menu_item') {
+		// Get this menu item's parent
+		$parent_menu_id = (int)get_post_meta ( $post->ID, '_menu_item_menu_item_parent', true );
+
+		// Move all children of this nav menu to the parent
+		$children_query = $wpdb->prepare("UPDATE $wpdb->postmeta SET meta_value = %d WHERE meta_key = '_menu_item_menu_item_parent' AND meta_value=%s", $parent_menu_id, $post->ID);
+		$children = $wpdb->query ( $children_query );
+	}
+
 	// Do raw query. wp_get_post_revisions() is filtered.
 	$revision_ids = $wpdb->get_col( $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE post_parent = %d AND post_type = 'revision'", $postid ) );
 	// Use wp_delete_post (via wp_delete_post_revision) again. Ensures any meta/misplaced data gets cleaned up.