How to submit a form using CTRL+S

I have a form I want to submit when the user presses CTRL+S.

In the submit button of the form I have the dmx-on:keydown.ctrl.keys line, but I can’t seem to make it activate… am I missing something about how this works, or something that could stop it activating?

<form novalidate="" id="f_message_template"...>
...
   <button class=" button_save" id="b_save_message_template" type="submit" dmx-on:keydown.ctrl.keys="f_message_template.submit()">{{apptext.value.400}}</button>
...
</form>

Thanks in anticipation!
Antony.