diff --git a/check_json.pl b/check_json.pl
index fb253c9..2330f63 100755
--- a/check_json.pl
+++ b/check_json.pl
@@ -139,8 +139,14 @@ my $json_response = decode_json($response->content);
 if ($np->opts->verbose) { (print Dumper ($json_response))};
 
 my @attributes = split(',', $np->opts->attributes);
-my @warning = split(',', $np->opts->warning);
-my @critical = split(',', $np->opts->critical);
+my @warning;
+if ($np->opts->warning) {
+    @warning = split(',', $np->opts->warning);
+}
+my @critical;
+if ($np->opts->critical) {
+    @critical = split(',', $np->opts->critical);
+}
 my @divisor = $np->opts->divisor ? split(',',$np->opts->divisor) : () ;
 my %attributes = map { $attributes[$_] => { warning => $warning[$_] , critical => $critical[$_], divisor => ($divisor[$_] or 0) } } 0..$#attributes;