diff --git a/library/Icingadb/Util/PerfData.php b/library/Icingadb/Util/PerfData.php
index 2d83c540..eccafc54 100644
--- a/library/Icingadb/Util/PerfData.php
+++ b/library/Icingadb/Util/PerfData.php
@@ -426,13 +426,17 @@ class PerfData
         $parts = explode(';', $this->perfdataValue);
 
         $matches = array();
-        if (preg_match('@^(-?(?:\d+)?(?:\.\d+)?)([a-zA-Z%°]{1,3})$@u', $parts[0], $matches)) {
+        if (preg_match('@^(U|-?(?:\d+)?(?:\.\d+)?)([a-zA-TV-Z%°]{1,3})$@u', $parts[0], $matches)) {
             $this->unit = $matches[2];
             $this->value = $matches[1];
         } else {
             $this->value = $parts[0];
         }
 
+        if (! is_numeric($this->value)) {
+            $this->value = null;
+        }
+
         switch (count($parts)) {
             /* @noinspection PhpMissingBreakStatementInspection */
             case 5: