diff --git a/library/Zend/Mail/Protocol/Smtp.php b/library/Zend/Mail/Protocol/Smtp.php
index 0800e3b00c..ca365e8958 100644
--- a/library/Zend/Mail/Protocol/Smtp.php
+++ b/library/Zend/Mail/Protocol/Smtp.php
@@ -197,7 +197,7 @@ public function helo($host = '127.0.0.1')
             if (!stream_socket_enable_crypto(
                 $this->_socket,
                 true,
-                STREAM_CRYPTO_METHOD_TLS_CLIENT|STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT|STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT
+                STREAM_CRYPTO_METHOD_TLS_CLIENT|STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT|STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT|STREAM_CRYPTO_METHOD_TLSv1_3_CLIENT
             )) {
                 /**
                  * @see Zend_Mail_Protocol_Exception