diff --git a/phpseclib/Crypt/Common/SymmetricKey.php b/phpseclib/Crypt/Common/SymmetricKey.php
index 76019337..e38cfaec 100644
--- a/phpseclib/Crypt/Common/SymmetricKey.php
+++ b/phpseclib/Crypt/Common/SymmetricKey.php
@@ -237,7 +237,7 @@ abstract class SymmetricKey
      * @var string
      * @access private
      */
-    private $iv = false;
+    protected $iv = false;
 
     /**
      * A "sliding" Initialization Vector
diff --git a/phpseclib/Crypt/Rijndael.php b/phpseclib/Crypt/Rijndael.php
index fb1edcf6..91c3b5c6 100644
--- a/phpseclib/Crypt/Rijndael.php
+++ b/phpseclib/Crypt/Rijndael.php
@@ -59,6 +59,7 @@ use phpseclib3\Crypt\Common\BlockCipher;
 use phpseclib3\Common\Functions\Strings;
 use phpseclib3\Exception\BadModeException;
 use phpseclib3\Exception\InsufficientSetupException;
+use phpseclib3\Exception\InconsistentSetupException;
 use phpseclib3\Exception\BadDecryptionException;
 
 /**
@@ -490,6 +491,45 @@ class Rijndael extends BlockCipher
         return pack('N*', ...$temp);
     }
 
+    /**
+     * Setup the self::ENGINE_INTERNAL $engine
+     *
+     * (re)init, if necessary, the internal cipher $engine and flush all $buffers
+     * Used (only) if $engine == self::ENGINE_INTERNAL
+     *
+     * _setup() will be called each time if $changed === true
+     * typically this happens when using one or more of following public methods:
+     *
+     * - setKey()
+     *
+     * - setIV()
+     *
+     * - disableContinuousBuffer()
+     *
+     * - First run of encrypt() / decrypt() with no init-settings
+     *
+     * {@internal setup() is always called before en/decryption.}
+     *
+     * {@internal Could, but not must, extend by the child Crypt_* class}
+     *
+     * @see self::setKey()
+     * @see self::setIV()
+     * @see self::disableContinuousBuffer()
+     * @access private
+     */
+    protected function setup()
+    {
+        if (!$this->changed) {
+            return;
+        }
+
+        parent::setup();
+
+        if (is_string($this->iv) && strlen($this->iv) != $this->block_size) {
+            throw new InconsistentSetupException('The IV length (' . strlen($this->iv) . ') does not match the block size (' . $this->block_size . ')');
+        }
+    }
+
     /**
      * Setup the key (expansion)
      *