===================================================================
RCS file: /cvs/mandoc/mandoc.1,v
retrieving revision 1.202
retrieving revision 1.203
diff -u -p -r1.202 -r1.203
--- mandoc/mandoc.1	2017/06/24 14:38:32	1.202
+++ mandoc/mandoc.1	2017/06/24 15:59:50	1.203
@@ -1,4 +1,4 @@
-.\"	$Id: mandoc.1,v 1.202 2017/06/24 14:38:32 schwarze Exp $
+.\"	$Id: mandoc.1,v 1.203 2017/06/24 15:59:50 schwarze Exp $
 .\"
 .\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2012, 2014-2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -816,6 +816,12 @@ macro does not use CVS
 keyword substitution, but using it is conventionally expected in the
 .Ox
 base system.
+.It Sy "operating system explicitly specified"
+.Pq mdoc , Ox , Nx
+The
+.Ic \&Os
+macro has an argument.
+In the base system, it is conventionally left blank.
 .It Sy "RCS id missing"
 .Pq Ox , Nx
 The manual page lacks the comment line with the RCS identifier