diff --git a/docs/configuration/configuration.md b/docs/configuration/configuration.md
index 4524fae6b..85e756b9d 100644
--- a/docs/configuration/configuration.md
+++ b/docs/configuration/configuration.md
@@ -63,5 +63,6 @@ advanced:
   elapsed: false
   # Availability timeout in seconds, disabled by default (0).
   # When enabled, devices will be checked if they are still online.
+  # Only AC powered routers are checked for availability.
   availability_timeout: 0
 ```