diff --git a/src/Data/Payload.php b/src/Data/Payload.php
index ede6f7f..6d232a1 100644
--- a/src/Data/Payload.php
+++ b/src/Data/Payload.php
@@ -19,9 +19,9 @@ final class Payload
     public static function decode(string $base64url): ?Payload
     {
         /* convert the base64url into json string */
-        $base64 = strtr($base64url, '-_', '+/');
-        $base64 .= str_repeat('=', (4 - strlen($base64) % 4) % 4);
-        $json = base64_decode($base64, true);
+        $json = base64_decode(str_pad(strtr($base64url, '-_', '+/'),
+            strlen($base64url) + strlen($base64url) % 4, '='
+        ), true);
         if ($json) {
             /* convert the json string into real data */
             $data = json_decode($json);