diff --git a/lib/libc/stdio/printf.3 b/lib/libc/stdio/printf.3
index 9a27f82c41d1..9b262e6bf8a0 100644
--- a/lib/libc/stdio/printf.3
+++ b/lib/libc/stdio/printf.3
@@ -1,4 +1,4 @@
-.\"	$NetBSD: printf.3,v 1.40 2005/07/20 13:31:15 christos Exp $
+.\"	$NetBSD: printf.3,v 1.41 2006/03/18 05:46:04 rumble Exp $
 .\"
 .\" Copyright (c) 1990, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -33,7 +33,7 @@
 .\"
 .\"     @(#)printf.3	8.1 (Berkeley) 6/4/93
 .\"
-.Dd July 20, 2005
+.Dd March 17, 2006
 .Dt PRINTF 3
 .Os
 .Sh NAME
@@ -132,6 +132,11 @@ If sufficient space cannot be allocated, these functions
 will return -1 and set
 .Fa ret
 to be a NULL pointer.
+Please note that these functions are not standardized, and not all
+implementations can be assumed to set the
+.Fa ret
+argument to NULL on error.
+It is more portable to check for a return value of -1 instead.
 .Pp
 .Fn snprintf
 and