diff --git a/cavegen.lua b/cavegen.lua
index 72d9f30..9d02834 100644
--- a/cavegen.lua
+++ b/cavegen.lua
@@ -7,12 +7,25 @@ fun_caves.cave_noise_2 = {offset = 0, scale = 1, seed = -8402, spread = {x = 40,
 local cave_noise_3 = {offset = 15, scale = 10, seed = 3721, spread = {x = 40, y = 40, z = 40}, octaves = 3, persist = 1, lacunarity = 2}
 
 
+local ground_nodes = {}
+ground_nodes[minetest.get_content_id('default:stone')] = true
+ground_nodes[minetest.get_content_id('default:desert_stone')] = true
+ground_nodes[minetest.get_content_id('default:sandstone')] = true
+ground_nodes[minetest.get_content_id('default:dirt')] = true
+ground_nodes[minetest.get_content_id('default:sand')] = true
+ground_nodes[minetest.get_content_id('default:dirt_with_grass')] = true
+ground_nodes[minetest.get_content_id('default:dirt_with_snow')] = true
+ground_nodes[minetest.get_content_id('default:dirt_with_dry_grass')] = true
+
+
 fun_caves.cavegen = function(minp, maxp, data, area, node, heightmap, underzone)
 	local csize = vector.add(vector.subtract(maxp, minp), 1)
 	local map_max = {x = csize.x, y = csize.y + 2, z = csize.z}
 	local map_min = {x = minp.x, y = minp.y - 1, z = minp.z}
+	local return_heightmap = false
 
 	if not heightmap then
+		return_heightmap = true
 		heightmap = {}
 	end
 
@@ -39,7 +52,7 @@ fun_caves.cavegen = function(minp, maxp, data, area, node, heightmap, underzone)
 				height = - max_depth
 				local ivm2 = area:index(x, maxp.y + 8, z)
 				for y = maxp.y + 8, minp.y - 8, -1 do
-					if data[ivm2] ~= node['air'] and data[ivm2] ~= node['ignore'] then
+					if ground_nodes[data[ivm2]] then
 						height = (y < maxp.y + 8) and y or max_depth
 						break
 					end
@@ -103,5 +116,9 @@ fun_caves.cavegen = function(minp, maxp, data, area, node, heightmap, underzone)
 		end
 	end
 
-	return write, heightmap
+	if return_heightmap then
+		return write, heightmap
+	else
+		return write, nil
+	end
 end
diff --git a/mapgen.lua b/mapgen.lua
index 8213ee4..f1e47a9 100644
--- a/mapgen.lua
+++ b/mapgen.lua
@@ -388,8 +388,12 @@ local function generate(p_minp, p_maxp, seed)
 		fun_caves.fortress(minp, maxp, data, area, node)
 		write = true
 	else
-		local write1, write2, write3
-		write1, heightmap = fun_caves.cavegen(minp, maxp, data, area, node, heightmap, underzone)
+		local write1, write2, write3, h2
+		write1, h2 = fun_caves.cavegen(minp, maxp, data, area, node, heightmap, underzone)
+		if h2 then
+			heightmap = h2
+		end
+
 		write2, write_p2 = fun_caves.decogen(minp, maxp, data, p2data, area, node, heightmap, biome_ids, underzone)
 		write3 = fun_caves.treegen(minp, maxp, data, p2data, area, node)
 		write = write1 or write2 or write3