Why is Walkspeed not a valid memeber of humanoid?

I am getting an error saying "Walkspeed is not a valid member of humanoid" I am trying to give the player a speedboost when they have a sword equipped. here is my code. I know 70 lines of code might be too much to look through. I can shorten it to just the walkspeed part of the code if that is better

local speedboost = 1.25


local speedboost = 1.25
local damage = 30
local swingtime = 1
local combowindow = .5
 


local Handle = Tool:WaitForChild("Handle")
local event = Tool:WaitForChild("RemoteEvent")
local slashsound = Handle:WaitForChild("SlashSound")
local overheadsound = Handle:WaitForChild("OverSound")
local lungesound = Handle:WaitForChild("LungeSound")
local lastclick = tick()
local combo = 0



Handle.Touched:Connect(function(hit)
	if equipped and character and humanoid and humanoid.Health > 0 and hit and hit:isDecendantOf(character)then
		local targethumanoid = hit.Parent:FindFirstChild("Humanoid")
		if targethumanoid and targethumanoid.Health > 0 and not hithumanoids[targethumanoid] then
			hithumanoids[targethumanoid] = true 
			targethumanoid:TakeDamage(damage * combo)
		end
	end
end)

Tool.Activated:connect(function()
	local clickdelta = tick() - lastclick
	if clickdelta > swingtime then
	lastclick = tick()
	   hithumanoids = {}
	if clickdelta < swingtime + combowindow then
		combo = (combo + 1) % 3
		else
			combo = 0
	end
	if player then
		    if combo then 
			    event:FireClient(player, "RunAnimation", "SlashAnim2")
				slashsound:Play()
			elseif combo == 1 then
				event:FireClient(player, "RunAnimation", "ThrustAnim2")
				overheadsound:Play()
			elseif combo == 2 then
			event:FireClient(player, "RunAnimation", "OverheadAnim2")
			lungesound:Play()
	 	end
	 end
  end 
end)


Tool.Equipped:Connect(function()
	equipped = true 
	lastclick = tick()
	character = Tool.Parent 
	player = game.Players:GetPlayerFromCharacter(character)
	humanoid = character:FindFirstChild("Humanoid")
	if humanoid == nil then 
		humanoid.WalkSpeed = humanoid.Walkspeed + speedboost 
	else
		character = nil 
	end
end)

 Tool.Unequipped:Connect(function()
	equipped = false 
	if humanoid then 
		humanoid.WalkSpeed = humanoid.Walkspeed / speedboost 
	end
	character = nil 
	humanoid = nil 
end)