diff --git a/phpseclib/Crypt/AES.php b/phpseclib/Crypt/AES.php
index 4ebf07e5..616c362e 100644
--- a/phpseclib/Crypt/AES.php
+++ b/phpseclib/Crypt/AES.php
@@ -66,7 +66,7 @@
  * Include Crypt_Rijndael
  */
 if (!class_exists('Crypt_Rijndael')) {
-    require_once 'Rijndael.php';
+    require_once('Rijndael.php');
 }
 
 /**#@+