diff --git a/cbox-tree.d/usr/lib/cryptobox/check_smb_idle.sh b/cbox-tree.d/usr/lib/cryptobox/check_smb_idle.sh
index d03d1ba..ffb5c77 100755
--- a/cbox-tree.d/usr/lib/cryptobox/check_smb_idle.sh
+++ b/cbox-tree.d/usr/lib/cryptobox/check_smb_idle.sh
@@ -29,7 +29,7 @@ set -eu
 filter_ipt_rules()
 # get the input rules for smb datagram traffic
 {
-	iptables -L INPUT -vnx | grep -E "tcp upt:138|udp dpt:139"
+	iptables -L INPUT -vnx | grep -E "udp dpt:138|tcp dpt:139"
 }