Niagara align sprit to mesh orientation singularity

Hello,

When using the mesh orientation vector for facing, I want it to point to the world up vector (0, 0, 1). When I use a very small X or Y component, this works correctly:


However, when I use a purely up vector (i.e., set X and Y to 0), the sprite disappears:


Is this expected behavior that I’m misunderstanding, or is it a bug?