windows-uptime plugin - perfdata non guideline conform output

Expected Behavior

the plugin perfdata output should be usable for graphing with e.g. graphite. In my case no graph is generated. With other plugins the behavior is like expected.

Current Behavior

If the -u parameter is used, in my case to set the unit to "hour", an 'h' is append to the perfdata current value. No graph is available.

"c:\Program Files\ICINGA2\sbin\check_uptime.exe" -c 840 -u h -w 768 UPTIME OK 352h | uptime=352h;768;840;0;

Possible Solution

I think the reason for this could be, that graphite isn't able to generate a graph because the 'h' can't be handled. According to the Monitoring Plugin Guidelines the 'h' is not one of the UOM (unit of measurement)

Steps to Reproduce (for bugs)

Use the plugin with the default command object an these parameters uptime_win_crit: "840", uptime_win_unit: "h", uptime_win_warn: "768"

Context

Your Environment

Version used (icinga2 --version): v2.8.4
Operating System and version: Windows Server 2008r2 (agent) centos7 (server)
Icinga Web 2 version and modules (System - About): 2.5.3 / graphite 1.0.1 /
Config validation (icinga2 daemon -C):
If you run multiple Icinga 2 instances, the zones.conf file (or icinga2 object list --type Endpoint and icinga2 object list --type Zone) from all affected nodes.

Icinga / icinga2