diff --git a/phpseclib/Crypt/RSA.php b/phpseclib/Crypt/RSA.php
index ac9101ae..48192c58 100644
--- a/phpseclib/Crypt/RSA.php
+++ b/phpseclib/Crypt/RSA.php
@@ -966,7 +966,7 @@ class RSA
         if (!$rsa->load($key, $type)) {
             return false;
         }
-        unset($rsa->publicExponent);
+        $rsa->publicExponent = false;
 
         // don't overwrite the old key if the new key is invalid
         $this->load($rsa);