How do I /fill blocks in a certain direction in Minecraft 1.16?

So, I’m attempting to create an attack for a boss fight I’m making. The boss can spawn a square of redstone blocks and dispensers which contain arrows. I want the dispensers to face west.

So I type this command:

fill 1994 143 1972 dispenser{Facing:west,Items:[{id:"arrow",Count:64b,Slot:0b}],}

The result looks like:

The dispensers are facing north.

No matter what I put for Facing, the dispensers are always facing north and I can’t do anything about it.

Is there a way I can fix this?

Any help appreciated.

fill x1 y1 z1 x2 y2 z2 dispenser[facing=west]{Items:[...]}