Miscellaneous: Sacrificial Dagger can't be equipped in off hand

[Fromp]

I just purchased a Sacrificial Dagger for my mage (only a cheap item I know), it's listed in game as being Primary and Secondary, but my mage can only equip it in her main hand.

[Fromp]

I can't find how to delete this, I believe this is actually due to the fact that it counts as a weapon and therefore I would need to be able to have dual wield on a mage to use it in her off hand.