diff --git a/install_config/install/prerequisites.adoc b/install_config/install/prerequisites.adoc
index 1bb91c973a46..e1f593f06d8a 100644
--- a/install_config/install/prerequisites.adoc
+++ b/install_config/install/prerequisites.adoc
@@ -639,7 +639,7 @@ connections, and is only required if you have clustered etcd.
 * Port *1936* can still be inaccessible due to your iptables rules. Use the following to configure iptables to open port *1936*:
 +
 ----
-# iptables OS_FIREWALL_ALLOW -p tcp -m state --state NEW -m tcp \
+# iptables -A OS_FIREWALL_ALLOW -p tcp -m state --state NEW -m tcp \
     --dport 1936 -j ACCEPT
 ----