Metric's meter.count ruby variable name?

Elastic Stack Logstash
2

event['meter_name.count'] works fine for me (with Logstash 1.5).

input {
  stdin {}
}

filter {
  metrics {
    meter => "meter_name"
    add_tag => "metric"
  }
  ruby {
    code => "
      event['message'] = 'Current count is: ' + event['meter_name.count'].to_s
    "
  }
}

output {
  if "metric" in [tags] {
    stdout {
      codec => json_lines
    }
  }
}