diff --git a/docs/library/machine.Timer.rst b/docs/library/machine.Timer.rst
index 77a549b40b..d1709a8189 100644
--- a/docs/library/machine.Timer.rst
+++ b/docs/library/machine.Timer.rst
@@ -27,11 +27,12 @@ instead of this class.
 Constructors
 ------------
 
-.. class:: Timer(id, ...)
+.. class:: Timer(id, /, ...)
 
-   Construct a new timer object of the given id. Id of -1 constructs a
+   Construct a new timer object of the given ``id``. ``id`` of -1 constructs a
    virtual timer (if supported by a board).
-   
+   ``id`` shall not be passed as a keyword argument.
+
    See ``init`` for parameters of initialisation.
 
 Methods