Ember 1.1x key-press event not responding to backspace

I am forced to use an older version of Ember and need to perform an action when a user types into a text field.

I've bound the action either by:

or

Both of these fire, except when I press backspace / delete to remove values. I need to event to fire in this use case.

Some googling turns up people suggesting using key-up or key-down but when I bind to those events in the same way as I've shown above, my action is never fired.

It feels like I'm missing something stupid here, any input would be greatly appreciated.

I'm afraid upgrading the Ember version is not an option.