diff --git a/modules/monitoring/library/Monitoring/Plugin/Perfdata.php b/modules/monitoring/library/Monitoring/Plugin/Perfdata.php
index 559e2a703..6c2d89a72 100644
--- a/modules/monitoring/library/Monitoring/Plugin/Perfdata.php
+++ b/modules/monitoring/library/Monitoring/Plugin/Perfdata.php
@@ -323,14 +323,14 @@ class Perfdata
             case 3:
                 $this->rawCriticalThreshold = trim($parts[2]);
                 $this->criticalThreshold = self::convert(
-                    ThresholdRange::fromString($this->rawCriticalThreshold ?: '~:'),
+                    ThresholdRange::fromString($this->rawCriticalThreshold),
                     $this->unit
                 );
                 // Fallthrough
             case 2:
                 $this->rawWarningThreshold = trim($parts[1]);
                 $this->warningThreshold = self::convert(
-                    ThresholdRange::fromString($this->rawWarningThreshold ?: '~:'),
+                    ThresholdRange::fromString($this->rawWarningThreshold),
                     $this->unit
                 );
         }
diff --git a/modules/monitoring/library/Monitoring/Plugin/ThresholdRange.php b/modules/monitoring/library/Monitoring/Plugin/ThresholdRange.php
index 26165c0e9..536dc8f7a 100644
--- a/modules/monitoring/library/Monitoring/Plugin/ThresholdRange.php
+++ b/modules/monitoring/library/Monitoring/Plugin/ThresholdRange.php
@@ -36,10 +36,14 @@ class ThresholdRange
      *
      * @return  ThresholdRange
      */
-    public static function fromString($rawRange)
+    public static function fromString($rawRange = '')
     {
         $range = new static();
 
+        if ($rawRange === '') {
+            return $range;
+        }
+
         $rawRange = ltrim($rawRange);
         if (substr($rawRange, 0, 1) === '@') {
             $range->setInverted();