===================================================================
RCS file: /cvs/mandoc/html.c,v
retrieving revision 1.191
retrieving revision 1.192
diff -u -p -r1.191 -r1.192
--- mandoc/html.c	2015/10/13 22:59:54	1.191
+++ mandoc/html.c	2016/01/04 12:45:29	1.192
@@ -1,4 +1,4 @@
-/*	$Id: html.c,v 1.191 2015/10/13 22:59:54 schwarze Exp $ */
+/*	$Id: html.c,v 1.192 2016/01/04 12:45:29 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2011, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2011-2015 Ingo Schwarze <schwarze@openbsd.org>
@@ -720,8 +720,8 @@ void
 bufcat_id(struct html *h, const char *src)
 {
 
-	/* Cf. <http://www.w3.org/TR/html4/types.html#h-6.2>. */
+	/* Cf. <http://www.w3.org/TR/html5/dom.html#the-id-attribute>. */
 
-	while ('\0' != *src)
-		bufcat_fmt(h, "%.2x", *src++);
+	for (; '\0' != *src; src++)
+		bufncat(h, *src == ' ' ? "_" : src, 1);
 }