diff --git a/README.md b/README.md
index d851d24..9e6e169 100644
--- a/README.md
+++ b/README.md
@@ -144,8 +144,8 @@ both IPv4 and IPv6 usage.
 #### Using iptables
 
 ```
-iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
-ip6tables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
+iptables -t nat -A POSTROUTING -o eth0 -i tun0 -j MASQUERADE
+ip6tables -t nat -A POSTROUTING -o eth0 -i tun0 -j MASQUERADE
 ```
 
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