diff --git a/library/ssl_invasive.h b/library/ssl_invasive.h
index 49ee83f..2a8d6b5 100644
--- a/library/ssl_invasive.h
+++ b/library/ssl_invasive.h
@@ -42,9 +42,11 @@
  * max_data_len bytes from \p data.
  *
  * \param ctx               The HMAC context. It must have keys configured
- *                          with mbedtls_md_hmac_starts(). It is reset using
- *                          mbedtls_md_hmac_reset() after the computation is
- *                          complete to prepare for the next computation.
+ *                          with mbedtls_md_hmac_starts() and use one of the
+ *                          following hashes: SHA-384, SHA-256, SHA-1 or MD-5.
+ *                          It is reset using mbedtls_md_hmac_reset() after
+ *                          the computation is complete to prepare for the
+ *                          next computation.
  * \param add_data          The additional data prepended to \p data. This
  *                          must point to a readable buffer of \p add_data_len
  *                          bytes.