===================================================================
RCS file: /cvs/mandoc/eqn_html.c,v
retrieving revision 1.16
retrieving revision 1.19
diff -u -p -r1.16 -r1.19
--- mandoc/eqn_html.c	2017/07/08 14:51:04	1.16
+++ mandoc/eqn_html.c	2019/03/17 18:21:45	1.19
@@ -1,4 +1,4 @@
-/*	$Id: eqn_html.c,v 1.16 2017/07/08 14:51:04 schwarze Exp $ */
+/*	$Id: eqn_html.c,v 1.19 2019/03/17 18:21:45 schwarze Exp $ */
 /*
  * Copyright (c) 2011, 2014 Kristaps Dzonsons <kristaps@bsd.lv>
  * Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -26,6 +26,8 @@
 #include <string.h>
 
 #include "mandoc.h"
+#include "roff.h"
+#include "eqn.h"
 #include "out.h"
 #include "html.h"
 
@@ -230,6 +232,9 @@ void
 print_eqn(struct html *p, const struct eqn_box *bp)
 {
 	struct tag	*t;
+
+	if (bp->first == NULL)
+		return;
 
 	t = print_otag(p, TAG_MATH, "c", "eqn");