diff --git a/include/mbedtls/chacha20.h b/include/mbedtls/chacha20.h
index f88bd28..7999702 100644
--- a/include/mbedtls/chacha20.h
+++ b/include/mbedtls/chacha20.h
@@ -133,9 +133,8 @@
  *
  *                  This function is used to both encrypt and decrypt data.
  *
- * \note            The \p input and \p output buffers may overlap, but only
- *                  if input >= output (i.e. only if input points ahead of
- *                  the output pointer).
+ * \note            The \p input and \p output pointers must either be equal or
+ *                  point to non-overlapping buffers.
  *
  * \note            mbedtls_chacha20_setkey and mbedtls_chacha20_starts must be
  *                  called at least once to setup the context before this function