diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index 8d41efffdc..fbb9633d2a 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -4923,7 +4923,7 @@ function sanitize_option( $option, $value ) {
 			break;
 
 		case 'timezone_string':
-			$allowed_zones = timezone_identifiers_list();
+			$allowed_zones = timezone_identifiers_list( DateTimeZone::ALL_WITH_BC );
 			if ( ! in_array( $value, $allowed_zones, true ) && ! empty( $value ) ) {
 				$error = __( 'The timezone you have entered is not valid. Please select a valid timezone.' );
 			}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index ef3997bdb0..25abc3a081 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-54228';
+$wp_version = '6.1-alpha-54229';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.