diff --git a/zabbix_scripts/check_zfs b/zabbix_scripts/check_zfs
index 071bfee..d333ff8 100644
--- a/zabbix_scripts/check_zfs
+++ b/zabbix_scripts/check_zfs
@@ -27,10 +27,10 @@ if (not $zpool or not $zfs){
   print 'ZBX_NOTSUPPOTED';
   exit 0;
 }
-if ($sanoidmon and not $sanoid){
+if (defined $sanoidmon and not $sanoid){
   die 'ZBX_NOTSUPPOTED';
 }
-if (not grep { $_ eq $sanoidmon } qw(snapshot capacity health)){
+if (defined $sanoidmon and not grep { $_ eq $sanoidmon } qw(snapshot capacity health)){
   die 'ZBX_NOTSUPPOTED';
 }