diff --git a/resources/check_resmon_metric b/resources/check_resmon_metric
index dda68457d8e029137c8c74b567a812c1264f06b2..1171f1db76a6f9b0eaeb647bfb217f22ce1def5b 100755
--- a/resources/check_resmon_metric
+++ b/resources/check_resmon_metric
@@ -374,6 +374,9 @@ eval {
     }
  
     if (defined $regex) {
+        if (!defined($value)) {
+          $value = '';
+        }
         if ($value =~ /$regex/) {
             $state = "OK";
         } else {