diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 4205a47..6b33cb5 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -414,7 +414,9 @@
  *               greater or equal than a needed length. If it is not the case, it
  *               returns #MBEDTLS_ERR_SSL_DECODE_ERROR error and pends a
  *               #MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR alert message.
- *               It is used to guaranteed remaining length.
+ *
+ *               This is a function-like macro. It is guaranteed to evaluate each
+ *               argument exactly once.
  *
  * \param cur    Pointer to the current position in the buffer.
  * \param end    Pointer to one past the end of the buffer.