diff --git a/src/Authorizer.php b/src/Authorizer.php
index 9e0689b..d2d2a2d 100644
--- a/src/Authorizer.php
+++ b/src/Authorizer.php
@@ -39,8 +39,9 @@ public static function sign($allowedResource, $authzgen, $handler = null)
         if (!isset(self::$globalSecret)) trigger_error('$globalSecret is not set', E_USER_WARNING);
 
         list($cerfiticateUrl, $timeStart, $timeEnd) = explode(';', $authzgen) + [null, null, null];
+        $opts = $handler !== null ? ['handler' => $handler] : [];
 
-        $publicKey = self::downloadSigningKey($cerfiticateUrl, ['handler' => $handler]);
+        $publicKey = self::downloadSigningKey($cerfiticateUrl, $opts);
 
         $resourceSecret = join(';', [
             $timeStart,