diff --git a/sys/sys/event.h b/sys/sys/event.h
index 46d845e097e..7ae1c9023ce 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -83,11 +83,11 @@
 struct kevent {
 	__uintptr_t	ident;		/* identifier for this event */
 	short		filter;		/* filter for event */
-	unsigned short	flags;
-	unsigned int	fflags;
-	__int64_t	data;
+	unsigned short	flags;		/* action flags for kqueue */
+	unsigned int	fflags;		/* filter flag value */
+	__int64_t	data;		/* filter data value */
 	void		*udata;		/* opaque user data identifier */
-	__uint64_t	ext[4];
+	__uint64_t	ext[4];		/* extensions */
 };
 
 #if defined(_WANT_FREEBSD11_KEVENT)