diff --git a/docs/library/uos.rst b/docs/library/uos.rst
index bb3c200177..e1ea72967f 100644
--- a/docs/library/uos.rst
+++ b/docs/library/uos.rst
@@ -88,8 +88,8 @@ Functions
 
 .. function:: urandom(n)
 
-   Return a bytes object with n random bytes, generated by the hardware
-   random number generator.
+   Return a bytes object with n random bytes. Whenever possible, it is
+   generated by the hardware random number generator.
 
 .. only:: port_wipy