Ferocious Roar [Ancestral Cry] cancelled on weapon set change

I use Ancestral Cry through Ferocious Roar while shapeshifted.

Ancestral Cry is set to Weapon Set II which trades skill speed for a longer duration on my Passive Skill Tree.

However, when I switch back to Weapon Set I, Ancestral Cry immediately cease. It does not come back if I re-switch to Weapon Set II.

I think the intended behaviour is that spells and effects remain active when you switch Weapon Set, otherwise there is not much point.