Welds for parts not working on skinned mesh rigs

Hey there, i need some help on this.

So, i decided to test out the new Skinned MeshParts feature… So, i made a test model…

But the problem comes when i animate it…
As you can see here, there are 2 welded MeshParts (wich are the glasses) to the head
But when i open the animation editor, the parts doesn’t moves with the head

What i tried so far

I used this method:

But it still not working…

I also used Welds instead WeldConstraints, but the result is the same.

Thanks for the help!