Can $__to and $__from variables be used instead of $timefilter

I would like to use the $__to and $__from variables instead of $timefilter. Trying this, I can get this query to work: “select value from table WHERE time > $__from and time < now()”

But this query returns N/A: “select value from table WHERE time > $__from and time < $__to”

Am I doing something wrong or is that query not supported. My version is Grafana v6.0.0 (34a9a62).

Thanks