diff --git a/README.md b/README.md
index 2486804..9797f7f 100644
--- a/README.md
+++ b/README.md
@@ -173,7 +173,7 @@ cargo run -p lanparty-gateway -- \
   --server-name lanparty-relay.local \
   --relay-ca-cert relay-cert.der \
   --room ROOM1 \
-  --iface eth0
+  --interface eth0
 ```
 
 The gateway first opens the wired LAN interface as an AF_PACKET socket with
diff --git a/TESTING.md b/TESTING.md
index 5c7ee52..649e1f1 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -90,11 +90,12 @@ sudo ./target/release/lanparty-gateway \
   --server-name lanparty-relay.local \
   --relay-ca-cert ./relay-cert.der \
   --room ROOM1 \
-  --iface eth0
+  --interface eth0
 ```
 
-Use the real wired LAN interface name for `--iface`. Do not use Wi-Fi. The
-gateway fails before joining the relay if sysfs reports no Ethernet carrier.
+Use the real wired LAN interface name for `--interface`. `--iface` is accepted
+as a shorter alias. Do not use Wi-Fi. The gateway fails before joining the
+relay if sysfs reports no Ethernet carrier.
 
 Expected gateway output: