diff --git a/USAGE.txt b/USAGE.txt
index 55da415997..01597418da 100644
--- a/USAGE.txt
+++ b/USAGE.txt
@@ -89,7 +89,7 @@ Options:
 
     After living for this timeout, a tunnel connection is retired: new streams
     are tunneled in new connections, and the old tunneled streams are forcibly
-    closed by the idle timeout if idle or by the tunnel timeout if not idle.
+    closed after being idle for one tenth of the idle timeout.
     And the retired connection is closed when all tunneled streams are closed.
     This setting helps with CGNAT networks where long-lived connections are
     stuck, but will break long-lived TCP protocols, e.g. SSH.