Miscellaneous: Wurmslayer won't fit into large sewing kits

[Pescador]

I just quested a Wurmslayer, and I have several large sewing kits with available slots in my inventory. Large sewing kits are listed as capacity: Giant, so they should be able to accomodate any item. When i try to place the Wurmslayer into one of them, I get the message "That item is too big to fit in that container."

When I try to drop it in my inventory, it falls to the ground.

I don't have any other giant capacity bags to test, so this could be an issue with the sewing kits or with the wurmslayer itself.