Prometheus Plugin Panic

[lswith]

System info:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.2 LTS"
Telegraf - version 0.13.1

Steps to reproduce:

1. reload telegraf config

2016/06/07 02:31:47 Reloading Telegraf config
2016/06/07 02:31:47 Hang on, flushing any cached metrics before shutdown
2016/06/07 02:31:47 Output [influxdb] buffer fullness: 0 / 1000 metrics. Total gathered metrics: 135674. Total dropped metrics: 0.
2016/06/07 02:31:47 Output [prometheus_client] buffer fullness: 0 / 1000 metrics. Total gathered metrics: 135674. Total dropped metrics: 0.
panic: http: multiple registrations for /metrics

goroutine 1 [running]:
panic(0xe84ec0, 0xc8207fc900)
        /usr/local/go/src/runtime/panic.go:481 +0x3e6
net/http.(*ServeMux).Handle(0xc820010ae0, 0x1240ea0, 0x8, 0x7f2b451911b0, 0xc820671770)
        /usr/local/go/src/net/http/server.go:1926 +0x297
net/http.Handle(0x1240ea0, 0x8, 0x7f2b451911b0, 0xc820671770)
        /usr/local/go/src/net/http/server.go:1961 +0x4b
github.com/influxdata/telegraf/plugins/outputs/prometheus_client.(*PrometheusClient).Start(0xc820690660, 0x0, 0x0)
        /home/ubuntu/telegraf-build/src/github.com/influxdata/telegraf/plugins/outputs/prometheus_client/prometheus_client.go:42 +0x7f
github.com/influxdata/telegraf/agent.(*Agent).Connect(0xc82015c548, 0x0, 0x0)
        /home/ubuntu/telegraf-build/src/github.com/influxdata/telegraf/agent/agent.go:53 +0x16a
main.main()
        /home/ubuntu/telegraf-build/src/github.com/influxdata/telegraf/cmd/telegraf/telegraf.go:237 +0x1c76