diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 6da4c70c6..cdcda30a1 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1277,7 +1277,8 @@ void mbedtls_ssl_conf_dbg( mbedtls_ssl_config *conf,
  * \param f_send   write callback
  * \param f_recv   read callback
  * \param f_recv_timeout blocking read callback with timeout.
- *                 The last argument is the timeout in milliseconds
+ *                 The last argument is the timeout in milliseconds,
+ *                 0 means no timeout
  *
  * \note           One of f_recv or f_recv_timeout can be NULL, in which case
  *                 the other is used. If both are non-NULL, f_recv_timeout is