diff --git a/install/prerequisites.adoc b/install/prerequisites.adoc
index 873cad51d86b..b0cc9672bb96 100644
--- a/install/prerequisites.adoc
+++ b/install/prerequisites.adoc
@@ -646,7 +646,7 @@ 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
 ----