diff --git a/phpseclib/Crypt/Base.php b/phpseclib/Crypt/Base.php
index d94d7517..d971e5a1 100644
--- a/phpseclib/Crypt/Base.php
+++ b/phpseclib/Crypt/Base.php
@@ -157,7 +157,7 @@ class Crypt_Base
      * @var string
      * @access private
      */
-    var $iv;
+    var $iv = '';
 
     /**
      * A "sliding" Initialization Vector