An arrangement is disclosed for providing an “end-stop” function for a variator in a continuously variable transmission. The variator (8) needs some arrangement for preventing its own drive ratio from going beyond a ratio limit. In accordance with the present invention, this is provided by means of a one-way clutch (22 or 24). The one-way clutch is coupled to both the variators input and its output, and is arranged to engage (lock up) when the variator reaches its ratio limit, so that the variator is prevented from going beyond the limits. The invention is particularly suited to use with transmissions which provide two regimes and a synchronous change between them.