diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index e243660..8629721 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -1506,9 +1506,15 @@
  *       1.3 support that this option enables.
  *
  * Requires: MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
+ * Requires: MBEDTLS_PSA_CRYPTO_C
+ *
+ * Note: even though TLS 1.3 depends on PSA Crypto, if you want it to only use
+ * PSA for all crypto operations, you need to also enable
+ * MBEDTLS_USE_PSA_CRYPTO; otherwise X.509 operations, and functions that are
+ * common with TLS 1.2 (record protection, running handshake hash) will still
+ * use non-PSA crypto.
  *
  * Uncomment this macro to enable the support for TLS 1.3.
- *
  */
 //#define MBEDTLS_SSL_PROTO_TLS1_3