diff --git a/include/mbedtls/net.h b/include/mbedtls/net.h
index ed2d5d3..92f94c0 100644
--- a/include/mbedtls/net.h
+++ b/include/mbedtls/net.h
@@ -178,6 +178,7 @@
  * \param buf      The buffer to write to
  * \param len      Maximum length of the buffer
  * \param timeout  Maximum number of milliseconds to wait for data
+ *                 0 means no timeout (wait forever)
  *
  * \return         the number of bytes received,
  *                 or a non-zero error code: