diff --git a/phpseclib/Crypt/DES.php b/phpseclib/Crypt/DES.php
index ce1a51e1..2181a489 100644
--- a/phpseclib/Crypt/DES.php
+++ b/phpseclib/Crypt/DES.php
@@ -1343,8 +1343,8 @@ class DES extends Base
                         $k[self::ENCRYPT][$i] = '$ke[' . $i . ']';
                         $k[self::DECRYPT][$i] = '$kd[' . $i . ']';
                     }
-                    $init_encrypt = '$ke = $self->keys[self::ENCRYPT];';
-                    $init_decrypt = '$kd = $self->keys[self::DECRYPT];';
+                    $init_encrypt = '$ke = $self->keys[$self::ENCRYPT];';
+                    $init_decrypt = '$kd = $self->keys[$self::DECRYPT];';
                     break;
             }