===================================================================
RCS file: /cvs/mandoc/html.c,v
retrieving revision 1.278
retrieving revision 1.279
diff -u -p -r1.278 -r1.279
--- mandoc/html.c	2022/07/06 14:34:59	1.278
+++ mandoc/html.c	2022/08/09 11:23:11	1.279
@@ -1,4 +1,4 @@
-/* $Id: html.c,v 1.278 2022/07/06 14:34:59 schwarze Exp $ */
+/* $Id: html.c,v 1.279 2022/08/09 11:23:11 schwarze Exp $ */
 /*
  * Copyright (c) 2008-2011, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2011-2015, 2017-2021 Ingo Schwarze <schwarze@openbsd.org>
@@ -403,10 +403,13 @@ html_make_id(const struct roff_node *n, int unique)
 	 * In addition, reserve '~' for ordinal suffixes.
 	 */
 
-	for (cp = buf; *cp != '\0'; cp++)
-		if (isalnum((unsigned char)*cp) == 0 &&
+	for (cp = buf; *cp != '\0'; cp++) {
+		if (*cp == ASCII_HYPH)
+			*cp = '-';
+		else if (isalnum((unsigned char)*cp) == 0 &&
 		    strchr("!$&'()*+,-./:;=?@_", *cp) == NULL)
 			*cp = '_';
+	}
 
 	if (unique == 0)
 		return buf;