Cannot get position shadow to appear in custom block

I am trying to create a custom block that spawns fireworks with a bang.
I want it to look something like this:


However, when I try to create the postion shadow, I just get a blank hole.

Here is my code so far:


/**
* Use this file to define custom functions and blocks.
* Read more at https://minecraft.makecode.com/blocks/custom
*/

/**
 * Custom blocks
 */
//% weight=100 color=#0fbc11 icon="✴"
namespace fireworks {
    /**
     * TODO: describe your function here
     * @param position: (0, 0, 0)
     * @param s describe parameter here, eg: "Hello"
     * @param e describe parameter here
     */
    //% blockId=fireworks_spawnFirework
    //% position.shadow=minecraftCreatePosition
    //% block="spawn firework at %position|with a bang %bang"



    export function spawnFirework(position: Position, bang: boolean): void {

    }
}

What am I doing wrong?

Nevermind. I solved the problem. I just needed to restart Minecraft to make it show up.