diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index ce95cec..462cf44 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -144,6 +144,9 @@
 #define MBEDTLS_SSL_TRANSPORT_DATAGRAM          1   /*!< DTLS     */
 
 #define MBEDTLS_SSL_MAX_HOST_NAME_LEN           255 /*!< Maximum host name defined in RFC 1035 */
+#define MBEDTLS_SSL_MAX_ALPN_NAME_LEN           255 /*!< Maximum size in bytes of a protocol name in alpn ext., RFC 7301 */
+
+#define MBEDTLS_SSL_MAX_ALPN_LIST_LEN           65535 /*!< Maximum size in bytes of list in alpn ext., RFC 7301          */
 
 /* RFC 6066 section 4, see also mfl_code_to_length in ssl_tls.c
  * NONE must be zero so that memset()ing structure to zero works */