diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 2c0684f..3f595a3 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -334,6 +334,8 @@
         } future_record;
 
     } buffering;
+
+    uint16_t mtu;                       /*!<  Handshake mtu, used to fragment outgoing messages */
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     /*