Mastery not working for DK ?

[Mysterix]

Guys i just switched two items with same stats except one has haste and the other has mastery ... normally the one with the mastery shld give me more shadow damage but it doesnt nthg change in the skills !! is mastery bugged for DK ?

[qwerty]

I just tested and seems both Frost/Unholy masteries are working. The tooltips for the spells/abilities wont update but if you attack something (training dummy in my case)

you'll notice more dmg  from frost/shadow spells with the mastery item on.