diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 2974057..02829e3 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -1444,27 +1444,29 @@
 }
 
 /*
- * State Handler : MBEDTLS_SSL_SERVER_CERTIFICATE
+ * Handler for MBEDTLS_SSL_SERVER_CERTIFICATE
  */
-int ssl_tls13_write_server_certificate( mbedtls_ssl_context *ssl )
+static int ssl_tls13_write_server_certificate( mbedtls_ssl_context *ssl )
 {
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
     int ret = mbedtls_ssl_tls13_write_certificate( ssl );
     if(ret != 0)
         return( ret );
-
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
     mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_VERIFY );
     return( 0 );
 }
 
 /*
- * State Handler : MBEDTLS_SSL_CERTIFICATE_VERIFY
+ * Handler for MBEDTLS_SSL_CERTIFICATE_VERIFY
  */
-int ssl_tls13_write_certificate_verify( mbedtls_ssl_context *ssl )
+static int ssl_tls13_write_certificate_verify( mbedtls_ssl_context *ssl )
 {
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
     int ret = mbedtls_ssl_tls13_write_certificate_verify( ssl );
     if(ret != 0)
         return( ret );
-
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
     mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED );
     return( 0 );
 }