diff --git a/src/php-8.1-strftime.php b/src/php-8.1-strftime.php
index d34f065..40eef9d 100644
--- a/src/php-8.1-strftime.php
+++ b/src/php-8.1-strftime.php
@@ -41,7 +41,7 @@ function strftime (string $format, $timestamp = null, ?string $locale = null) :
 
     $timestamp->setTimezone(new DateTimeZone(date_default_timezone_get()));
 
-    $locale = Locale::canonicalize($locale ?? setlocale(LC_TIME, '0'));
+    $locale = Locale::canonicalize($locale ?? (Locale::getDefault() ?? setlocale(LC_TIME, '0')));
 
     $intl_formats = [
       '%a' => 'ccc',	// An abbreviated textual representation of the day	Sun through Sat