LocalTransparencyModifier giving errors depsite it working

So i havent really seen any posts talking about this issue, where localtransparencymodifier seems to give an error whenever i use it, even tho its working perfectly fine!

Maybe its because my game is R6, but im not entirely sure. heres the piece of code im using:

RunService.RenderStepped:Connect(function()
	for _, rizz in pairs(character:GetChildren()) do
		if string.match(rizz.Name, "Arm") then
			rizz.LocalTransparencyModifier = 0
		end
	end
end)

and this is the error it gives:

and as you can see it works:

maybe i made a mistake? i dont know, thanks in advance.