diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 7cf677a..9b4ad3e 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1628,7 +1628,8 @@
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 && MBEDTLS_SSL_PROTO_TLS1_3 */
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3)
-extern const uint8_t mbedtls_ssl_tls13_hello_retry_request_magic[32];
+extern const uint8_t mbedtls_ssl_tls13_hello_retry_request_magic[
+                        MBEDTLS_SERVER_HELLO_RANDOM_LEN ];
 int mbedtls_ssl_tls13_process_finished_message( mbedtls_ssl_context *ssl );
 int mbedtls_ssl_tls13_write_finished_message( mbedtls_ssl_context *ssl );
 void mbedtls_ssl_tls13_handshake_wrapup( mbedtls_ssl_context *ssl );