This script checks for banned text but it always returns false?

EDIT: It turns out it only DOESN'T work if the text contains spaces

I am making a SB game, and for the script executor it has a function that checks for banned functions. It doesn't seem to work. Could anyone help me?

-- List
local banned = {
	"TeleportService",
	"Teleport Service",
	"PlayerGui",
	"Players",
	"Lighting",
	"loadstring",
	"StarterGui",
	"FireServer",
	"InvokeServer",
	"Invoke",
	"Fire"
}

-- Function
checkIfBanned = function(text)
	for i=1,#banned do
		if string.find(string.lower(text),string.lower(banned[i])) ~= nil then
			warn('__Error: Code contains banned text')
			return true
		else
			warn('Code safe...')
			return false
		end
	end
end

-- Test call
print(checkIfBanned("Teleport Service")) -- Always prints "false" and I don't know why.

It's probably something obvious and I'm just stupid. Any help would be appreciated.