diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index b8361db..76962d3 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -307,6 +307,10 @@
       + ( MBEDTLS_SSL_CID_OUT_LEN_MAX ) )
 #endif
 
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+#define MBEDTLS_TLS1_3_MD_MAX_SIZE         MBEDTLS_MD_MAX_SIZE
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
 #if defined(MBEDTLS_SSL_MAX_FRAGMENT_LENGTH)
 /**
  * \brief          Return the maximum fragment length (payload, in bytes) for