--- a/term_tag.h
+++ b/term_tag.h
@@ -18,6 +18,8 @@
  * For use by the mandoc(1) ASCII and UTF-8 formatters only.
  */
 
+_Static_assert(sizeof("@TERMUX_PREFIX@/tmp/man.XXXXXXXXXX.html") <= 80, "tmpfile name too long");
+
 struct	tag_files {
 	char	 ofn[80];	/* Output file name. */
 	char	 tfn[80];	/* Tag file name. */
