diff --git a/lib/icinga/plugin/New-IcingaPerformanceDataEntry.psm1 b/lib/icinga/plugin/New-IcingaPerformanceDataEntry.psm1
index f0eeb74..79c6235 100644
--- a/lib/icinga/plugin/New-IcingaPerformanceDataEntry.psm1
+++ b/lib/icinga/plugin/New-IcingaPerformanceDataEntry.psm1
@@ -32,7 +32,7 @@ function New-IcingaPerformanceDataEntry()
 
     return ([string]::Format(
         "'{0}'={1}{2};{3};{4}{5}{6} ",
-        $LabelName,
+        $LabelName.ToLower(),
         (Format-IcingaPerfDataValue $PerfValue),
         $PerfDataObject.unit,
         (Format-IcingaPerfDataValue $PerfDataObject.warning),