1 files changed, 2 insertions, 1 deletions
diff --git a/libar2.h b/libar2.h
index f4f3412..144b430 100644
--- a/libar2.h
+++ b/libar2.h
@@ -543,7 +543,8 @@ size_t libar2_encode_params(char *buf, const struct libar2_argon2_parameters *pa
  * to a length divible by 4
  * 
  * @param   buf   Output buffer, or `NULL`
- * @param   data  The data to encode
+ * @param   data  The data to encode, may be
+ *                `NULL` if `buf` is `NULL`
  * @param   len   The number of bytes in `data`
  * @return        The number of bytes required for `buf`,
  *                including the NUL byte added to the end