diff --git a/lib/Crypto/AbstractCrypt.php b/lib/Crypto/AbstractCrypt.php
index c13e1b5..7ce1c94 100644
--- a/lib/Crypto/AbstractCrypt.php
+++ b/lib/Crypto/AbstractCrypt.php
@@ -56,8 +56,5 @@ abstract class AbstractCrypt extends AbstractAlgorithm
      *
      * @return string The salt string.
      */
-    protected function getSalt()
-    {
-        return "";
-    }
+    protected abstract function getSalt();
 }
diff --git a/lib/Crypto/Crypt.php b/lib/Crypto/Crypt.php
index c52be8d..609bdcb 100644
--- a/lib/Crypto/Crypt.php
+++ b/lib/Crypto/Crypt.php
@@ -56,4 +56,12 @@ class Crypt extends AbstractCrypt
     {
         return "Unix (Crypt)";
     }
+
+    /**
+     * Not used.
+     */
+    protected function getSalt()
+    {
+        return null;
+    }
 }