diff --git a/usr.bin/unifdef/unifdef.1 b/usr.bin/unifdef/unifdef.1
index 02cbfeba8ad..12a5438553f 100644
--- a/usr.bin/unifdef/unifdef.1
+++ b/usr.bin/unifdef/unifdef.1
@@ -308,10 +308,16 @@ in comment.
 The
 .Nm
 command appeared in
-.Bx 4.3 .
+.Bx 2.9 .
 .Tn ANSI\~C
 support was added in
 .Fx 4.7 .
+.Sh AUTHORS
+This implementation was originally written by
+.An Dave Yost Aq Dave@Yost.com .
+.An Tony Finch Aq dot@dotat.at
+rewrote it to support
+.Tn ANSI\~C .
 .Sh BUGS
 Expression evaluation is very limited.
 .Pp