Using coprocess to write a name referenced variable in BASH

I currently try to start background process with coproc and update a name reference variable. My not working code:

function updateVariable(){
  local -n myVar="${1}"
  #i=0;
  while :
  do
    sleep 1
    myVar="ok"
    #((++i))
  done
}

capture=""; coproc mycoproc { updateVariable capture; }

This does not work as I exspected.

$capture

is just empty. I would exspect it to be "ok". Thanks a lot!