diff --git a/wp-admin/admin-ajax.php b/wp-admin/admin-ajax.php
index 7317816736..4fb15fbdba 100644
--- a/wp-admin/admin-ajax.php
+++ b/wp-admin/admin-ajax.php
@@ -988,10 +988,12 @@ case 'autosave' : // The name of this action is hardcoded in edit_post()
 	break;
 case 'closed-postboxes' :
 	check_ajax_referer( 'closedpostboxes', 'closedpostboxesnonce' );
-	$closed = isset( $_POST['closed'] ) ? $_POST['closed'] : '';
-	$closed = explode( ',', $_POST['closed'] );
-	$hidden = isset( $_POST['hidden'] ) ? $_POST['hidden'] : '';
-	$hidden = explode( ',', $_POST['hidden'] );
+	$closed = isset( $_POST['closed'] ) ? explode( ',', $_POST['closed']) : array();
+	$closed = array_filter($closed);
+
+	$hidden = isset( $_POST['hidden'] ) ? explode( ',', $_POST['hidden']) : array();
+	$hidden = array_filter($hidden);
+
 	$page = isset( $_POST['page'] ) ? $_POST['page'] : '';
 
 	if ( !preg_match( '/^[a-z_-]+$/', $page ) )
diff --git a/wp-admin/includes/template.php b/wp-admin/includes/template.php
index 97d21a2a00..d8dfb600d3 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -2967,12 +2967,11 @@ function get_hidden_meta_boxes($screen) {
 	if ( is_string($screen) )
 		$screen = convert_to_screen($screen);
 
-	$hidden = (array) get_user_option( "meta-box-hidden_$screen->id" );
+	$hidden = get_user_option( "meta-box-hidden_$screen->id" );
 
 	// Hide slug boxes by default
-	if ( empty($hidden[0]) ) {
+	if ( !is_array($hidden) )
 		$hidden = array('slugdiv');
-	}
 
 	return $hidden;
 }