Makashi mastery and Guardian with Immune: Pierce keyword

[Task Master Wei]

When Count Dooku performs a melee attack against a clone trooper unit, while Obi-wan (benefiting from his 2-pip card) chooses to use his guardian keyword to cancel some attack dice.

During this attack, if Count Dooku chooses to trigger his Makashi Mastery, is Obi-wan still able to benefit from his immune: pierce?

[TalkPolite]

Hello,

Yes. The defender cannot use Impervious or Immune: Pierce, but Obi-Wan is not the defender while using Guardian. 

TP