diff --git a/mkdio.h.in b/mkdio.h.in
index badc1cc..70d91e3 100644
--- a/mkdio.h.in
+++ b/mkdio.h.in
@@ -42,6 +42,7 @@ enum {  MKD_NOLINKS=0,		/* don't do link processing, block <a> tags  */
 	MKD_LATEX,		/* handle embedded LaTeX escapes */
 	MKD_ALT_AS_TITLE,	/* use alt text as the title if no title is listed */
 	MKD_EXTENDED_ATTR,	/* allow extended attribute suffixes */
+	MKD_HTML5,		/* handle html5 tags (obsolete?) */
 	MKD_NR_FLAGS };
 
 /* abstract flag type */