diff --git a/lib/libc/gen/sysctl.3 b/lib/libc/gen/sysctl.3
index bb79856fb7a2..1e7ee36e5c91 100644
--- a/lib/libc/gen/sysctl.3
+++ b/lib/libc/gen/sysctl.3
@@ -1,4 +1,4 @@
-.\"	$NetBSD: sysctl.3,v 1.142 2004/12/27 13:35:47 christos Exp $
+.\"	$NetBSD: sysctl.3,v 1.143 2005/03/21 08:51:40 yamt Exp $
 .\"
 .\" Copyright (c) 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -1103,10 +1103,7 @@ the MTU of the appropriate interface.
 Otherwise, it is calculated based on the greater of the MTU of the
 interface, and the largest (non-loopback) interface MTU on the system.
 .It Li tcp.sack
-TCP Selective ACKnowledgement (RFC 2018) is not implemented in
-.Nx
-at this time.
-Changing this value will have no effect.
+Returns 1 if RFC 2018 Selection ACKnowledgement is enabled.
 .It Li tcp.win_scale
 If rfc1323 is enabled, a value of 1 indicates RFC 1323 window scale options,
 for increasing the TCP window size, are enabled.