Why is my anti speed hack not working?

I recently put in a local script this code in startercharacterscripts:

humanoid:GetPropertyChangedSignal("WalkSpeed"):Connect(function() 
	if humanoid.WalkSpeed ~= 16 then
		player:Kick()
	end
end)

but it doesn't work at all on the exploiter, they keep changing their walkspeed to like 100 and the script is not detecting them at all. There's more to the script with detecting other stuff but none of it works on the exploiter, it's like the whole script is not detecting them. Is there any way I can fix this anti exploit?

Why don't you do like:

humanoid.Changed:connect(function()
if humanoid.WalkSpeed ~= 16 then
player:Kick("Error occured: Walkspeed changed")
end
end)