Terrain scripting help

I'm trying to make a terrain building tool, and I need help. This script isn't working.

The output says that on Line 10, Argument 6 is missing or nil.

local deb = false
print("waht")
script.Parent.Equipped:connect(function(mouse)
    print"lol" 
    mouse.Button1Down:connect(function()
        print("running")
        if deb ~= true then
            deb = true
            local dacell = Workspace.Terrain:WorldToCellPreferEmpty(Vector3.new(mouse.Hit.p))
            local actcell = Workspace.Terrain:SetCell(dacell,Enum.CellMaterial.Cement,Enum.CellOrientation.X)
            wait(1)
            deb = false
        end
    end)
end)

17:23:14.438 - Argument 6 missing or nil
17:23:14.438 - Script 'Players.Player1.Backpack.Tool.LocalScript', Line 10
17:23:14.438 - stack end
17:23:14.439 - Disconnected event because of exception