Faster Attacks sockable despite lacking Dexterity

My character lacks 2 Dexterity to use a Level 2 Faster Attacks but could apparently level and can socket the Gem into his armor.
Additionaly the armor still provides its stats and doesnt get unuseable by socketing the gem into it.

Only when the gem is already socketed in the armor and I unequip it, it won't let me put it back on.

Here some screenshots:

The gem:


Equipped gem:


Gem in unequipped armor:

Look at your amulet.

Ohhh i see, completely missed that.

Thanks for pointing out.

So no bug here, luckily.