diff --git a/phpseclib/Crypt/DES.php b/phpseclib/Crypt/DES.php
index 5b141d18..b274495b 100644
--- a/phpseclib/Crypt/DES.php
+++ b/phpseclib/Crypt/DES.php
@@ -674,9 +674,11 @@ class Crypt_DES extends Crypt_Base
      */
     function isValidEngine($engine)
     {
-        if ($engine == CRYPT_ENGINE_OPENSSL) {
-            $this->cipher_name_openssl_ecb = 'des-ecb';
-            $this->cipher_name_openssl = 'des-' . $this->_openssl_translate_mode();
+        if ($this->key_size_max == 8) {
+            if ($engine == CRYPT_ENGINE_OPENSSL) {
+                $this->cipher_name_openssl_ecb = 'des-ecb';
+                $this->cipher_name_openssl = 'des-' . $this->_openssl_translate_mode();
+            }
         }
 
         return parent::isValidEngine($engine);