diff --git a/bin/rrd-extractstats.pl b/bin/rrd-extractstats.pl
index 9a824ab..a729720 100755
--- a/bin/rrd-extractstats.pl
+++ b/bin/rrd-extractstats.pl
@@ -43,7 +43,7 @@ $|=1;
 my $i :shared = 0;
 
 my $num_workers	= 1;
-if (($ENV{'THREADS'} =~ /^\d+$/) and ($ENV{'THREADS'} > 0)) { 
+if (($ENV{'THREADS'}) and ($ENV{'THREADS'} =~ /^\d+$/) and ($ENV{'THREADS'} > 0)) { 
     $num_workers = $ENV{'THREADS'};
 }
 print("Using " . $num_workers . " threads.\n");