diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index 102deab448..3c07900a72 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -734,6 +734,9 @@ class wpdb {
 	 * @since 3.1.0
 	 */
 	public function init_charset() {
+		$charset = '';
+		$collate = '';
+
 		if ( function_exists('is_multisite') && is_multisite() ) {
 			$charset = 'utf8';
 			if ( defined( 'DB_COLLATE' ) && DB_COLLATE ) {