['For' loop issue] Can someone just explain to me why this is giving an error?

I am at a loss here. It looks fine to me.

I should know how to fix simple issues like this, but I am lost.

I am getting an error for something that should be somewhat simple. Can someone please point out the possible issue. I have fooled around with this for a bit now and cannot figure out the problem.

for x = 100, x > 85, -5 do
		game.StarterGui.Rain.Dark.BackgroundTransparency = x / 100
end

The error:

22:22:31.718 - ServerScriptService.Rain:6: attempt to compare number with nil

Thanks