diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index b9c896f..328d2ab 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1408,6 +1408,7 @@
  * module to perform private key operations instead of performing the
  * operation inside the library.
  *
+ * Requires: MBEDTLS_X509_CRT_PARSE_C
  */
 //#define MBEDTLS_SSL_ASYNC_PRIVATE