diff --git a/library/bignum.c b/library/bignum.c
index 76202fe..521787d 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1933,10 +1933,9 @@
 
 /*
  * Fill X with size bytes of random.
- *
- * Use a temporary bytes representation to make sure the result is the same
- * regardless of the platform endianness (useful when f_rng is actually
- * deterministic, eg for tests).
+ * The bytes returned from the RNG are used in a specific order which
+ * is suitable for deterministic ECDSA (see the specification of
+ * mbedtls_mpi_random() and the implementation in mbedtls_mpi_fill_random()).
  */
 int mbedtls_mpi_fill_random( mbedtls_mpi *X, size_t size,
                      int (*f_rng)(void *, unsigned char *, size_t),