diff --git a/phpseclib/Crypt/AES.php b/phpseclib/Crypt/AES.php
index fd4935a3..8b1efd4b 100644
--- a/phpseclib/Crypt/AES.php
+++ b/phpseclib/Crypt/AES.php
@@ -412,10 +412,10 @@ class Crypt_AES extends Crypt_Rijndael {
                 if ($last_pos) {
                     $plaintext = mdecrypt_generic($this->demcrypt, substr($ciphertext, 0, $last_pos));
                     $this->decryptIV = substr($ciphertext, $last_pos - 16, 16);
-                    $this->decryptIV = mcrypt_generic($this->ecb, $this->decryptIV);
                 }
 
                 if (strlen($ciphertext) & 0xF) {
+                    $this->decryptIV = mcrypt_generic($this->ecb, $this->decryptIV);
                     $buffer = substr($ciphertext, $last_pos);
                     $plaintext.= $buffer ^ $this->decryptIV;
                 }