Help?? The output says "Walkspeed is not a valid member of Humanoid"

So, for however long you hold the left mouse button, the players walkspeed increases however long you hold it. It just errors out. Please help!!

Player = game.Players.LocalPlayer
Character = Player.Character
Torso = Character.Torso
Mouse = Player:GetMouse()
hold = false

Mouse.Button1Down:connect(function()
	
	if hold == false then
		hold = true
		while hold == true do
			Player.Character.Humanoid.Walkspeed = Player.Character.Humanoid.Walkspeed +1
	local	Brick = Instance.new("Part", Player)
			Brick.Position = Player.Position
			Brick.BrickColor = BrickColor.new("New Yeller")
			Brick.Transparency = 0.7
			
		end
	end

end)



Mouse.Button1Up:connect(function()
	if hold == true then
		hold = false
	end
end)

It's "WalkSpeed", not "Walkspeed".