Marking Macros /mk attack & /mk off

I primarily use "/mk attack" to mark targets as it marks each subsequent mob with a new number. For instance, if a mob is already marked as "1", the next mob I mark will by default be "2". Its very helpful.

My issue isn't with the /mk attack macro, its the /mk off command that has me scratching my head. Pre-2.1 "/mk off" worked perfectly fine. Since 2.1 dropped it hasn't worked. I am given a prompt in the game that it is an 'improper' command.

Due to the mechanics of the /mk attack macro, there are numerous times where I'll be rushing through a dungeon and go to mark the next set of mobs but it'll skip marks 1 and 2 and go straight to 3 and 4. Not the end of the world, but it can get confusing. In circumstances such as this /mk off acts as an eraser of sorts.

I was just curious if anyone knows of a macro to clear currently marked targets, or if my macro is wrong. The macro itself is simply, "/mk off".