How do I put a user's thumbnail on a decal?

I'm making a script that puts the user's player thumbnail on a decal but it doesn't seem to be working. The script is a LocalScript located in the decal. Here is my code:

local Players = game:GetService("Players")

local player = Players.LocalPlayer

-- Fetch the thumbnail
local userId = player.UserId
local thumbType = Enum.ThumbnailType.HeadShot
local thumbSize = Enum.ThumbnailSize.Size420x420
local content, isReady = Players:GetUserThumbnailAsync(userId, thumbType, thumbSize)

-- Set the Decal's content to the user thumbnail
local Decal = script.Parent
Decal.Texture = content