diff --git a/tcp_syni.nim b/tcp_syni.nim
index 01335c5..efde0a8 100644
--- a/tcp_syni.nim
+++ b/tcp_syni.nim
@@ -23,7 +23,7 @@ type
 
 proc addFirewallRule(srcIp: IpAddress, srcPort: Port,
                      dstIp: IpAddress, dstPort: Port) {.async.} =
-  let firewall_cmd = fmt"""iptables -A INPUT \
+  let firewall_cmd = fmt"""iptables -I INPUT \
   -d {srcIp} \
   -p icmp \
   --icmp-type time-exceeded \