diff --git a/mods/MAPGEN/mcl_mapgen_core/init.lua b/mods/MAPGEN/mcl_mapgen_core/init.lua
index 05c88cf5..965a46f5 100644
--- a/mods/MAPGEN/mcl_mapgen_core/init.lua
+++ b/mods/MAPGEN/mcl_mapgen_core/init.lua
@@ -1,4 +1,9 @@
-mcl_mapgen_core = {}
+mcl_mapgen_core = {
+	replace_nether_roof_void_with_air = minetest.settings:get_bool(
+		"mcl_mapgen_core_replace_nether_roof_void_with_air",
+		false
+	)
+}
 mcl_mapgen_core.registered_generators = {}
 
 local lvm, nodes, param2 = 0, 0, 0
@@ -2296,3 +2301,24 @@ function mcl_mapgen_core.get_node(p, force, us_timeout)
 	return node
 	-- it still can return "ignore", LOL, even if force = true, but only after time out
 end
+
+
+if mcl_mapgen_core.replace_nether_roof_void_with_air then
+	minetest.register_lbm({
+		label = "Replace Nether roof void from MineClone2 <0.71 with air",
+		name = "mcl_mapgen_core:replace_nether_roof_void_with_air",
+		nodenames = { "mcl_core:void" },
+		run_at_every_load = false,
+		action = function(pos, node)
+			if (
+				pos.y >= mcl_vars.mg_bedrock_nether_top_max and
+				pos.y <= mcl_vars.mg_nether_max
+			) then
+				minetest.swap_node(
+					pos,
+					{ name="air" }
+				)
+			end
+		end,
+	})
+end
diff --git a/settingtypes.txt b/settingtypes.txt
index cd8201ac..0fa21993 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -152,3 +152,8 @@ basic_pseudobiome_villages (Enables very basic, and experimental "pseudobiome-ba
 
 # If enabled, will run an LBM to fix the top 1/2 of double plants in mcimported worlds; defaults to true.
 fix_doubleplants (Mcimport double plant fixes) bool true
+
+# If enabled, will run an LBM to replace void nodes on the Nether roof generated by MineClone2 <0.71 with air.
+# Activate this setting if you generated some Nether in MineClone2 <0.71 and want to build on the Nether roof.
+# WARNING: This setting has quite poor performance and may lag Minetest while affected areas are being fixed.
+mcl_mapgen_core_replace_nether_roof_void_with_air (Replace Nether roof void from MineClone2 <0.71 with air) bool false