diff --git a/phpseclib/Crypt/Random.php b/phpseclib/Crypt/Random.php
index e38bdf8d..8532aab5 100644
--- a/phpseclib/Crypt/Random.php
+++ b/phpseclib/Crypt/Random.php
@@ -46,9 +46,7 @@
  *
  * @access private
  */
-if (!defined('CRYPT_RANDOM_IS_WINDOWS')) {
-    define('CRYPT_RANDOM_IS_WINDOWS', strtoupper(substr(PHP_OS, 0, 3)) === 'WIN');
-}
+define('CRYPT_RANDOM_IS_WINDOWS', strtoupper(substr(PHP_OS, 0, 3)) === 'WIN');
 
 /**
  * Generate a random string.