diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 5238f04..86f44cb 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -29,6 +29,7 @@
 
 int mbedtls_ssl_tls13_handshake_server_step( mbedtls_ssl_context *ssl )
 {
+    ((void) ssl);
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "tls1_3 server state: %d", ssl->state ) );
 
     return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );