diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index fba8f8f84..89cc0513e 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1124,7 +1124,9 @@ struct mbedtls_ssl_session
      * to be studied whether one of them can be removed. */
     unsigned char MBEDTLS_PRIVATE(minor_ver);    /*!< The TLS version used in the session. */
 
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
     mbedtls_ssl_tls1_3_application_secrets MBEDTLS_PRIVATE(app_secrets);
+#endif
 
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 #if defined(MBEDTLS_SSL_KEEP_PEER_CERTIFICATE)