diff --git a/homeassistant/components/device_tracker/asuswrt.py b/homeassistant/components/device_tracker/asuswrt.py
index 37e8cb0b2e7..76a501f8b80 100644
--- a/homeassistant/components/device_tracker/asuswrt.py
+++ b/homeassistant/components/device_tracker/asuswrt.py
@@ -34,7 +34,7 @@ PLATFORM_SCHEMA = vol.All(
         vol.Required(CONF_USERNAME): cv.string,
         vol.Optional(CONF_PASSWORD): cv.string,
         vol.Optional(CONF_PROTOCOL, default='ssh'):
-            vol.Schema(['ssh', 'telnet']),
+            vol.In(['ssh', 'telnet']),
         vol.Optional(CONF_MODE, default='router'):
             vol.Schema(['router', 'ap']),
         vol.Optional(CONF_SSH_KEY): cv.isfile,