gistfile1.diff

diff --git a/init.lua b/init.lua
index f6e2a79..aa15f99 100644
--- a/init.lua
+++ b/init.lua
@@ -395,7 +395,9 @@ minetest.register_on_generated(function(minp, maxp, seed)
        end
        local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
        local data = vm:get_data()
-       for i,d in ipairs(data) do
+       local area = VoxelArea:new{emin, emax}
+       for i in area:iterp(minp, maxp) do
+               local d = data[i]
                if d == air or d == stone_with_coal or d == stone_with_iron then
                        data[i] = air
                elseif d == stone_with_mese or d == stone_with_diamond or d == lava_source then