invalid argument #2 to 'random' (interval is empty)?

Hello. Im new to tables and im trying to make a system of a random number being pulled from a table but i get the error. " invalid argument #2 to 'random' (interval is empty)". Any help is thankful.

local lengths = {
	Short = 100,
	Medium = 500,	
	Long = 1000
}

local length = math.random(1,#lengths)


while wait(2) do
	print(lengths[length])
end