diff --git src/wp-admin/includes/class-wp-list-table.php src/wp-admin/includes/class-wp-list-table.php
index f31f4eaed6..c29518a1ec 100644
--- src/wp-admin/includes/class-wp-list-table.php
+++ src/wp-admin/includes/class-wp-list-table.php
@@ -905,7 +905,7 @@ foreach ( $this->modes as $mode => $title ) {
 
 	/**
 	 * Get a list of sortable columns. The format is:
-	 * 'internal-name' => 'orderby'
+	 * 'internal-name' => array( 'orderby' )
 	 * or
 	 * 'internal-name' => array( 'orderby', true )
 	 *