diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 18982f8..6be684e 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -307,6 +307,7 @@
                                               resending messages             */
     unsigned char alt_out_ctr[8];       /*!<  Alternative record epoch/counter
                                               for resending messages         */
+    uint16_t mtu;                       /*!<  Handshake mtu, used to fragment outoing messages */
 #endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     /*