diff --git a/phpseclib/File/X509.php b/phpseclib/File/X509.php
index 5714deb8..1024122c 100644
--- a/phpseclib/File/X509.php
+++ b/phpseclib/File/X509.php
@@ -2714,6 +2714,7 @@ class File_X509 {
      */
     function setPublicKey($key)
     {
+        $key->setPublicKey();
         $this->publicKey = $key;
     }