diff --git a/df_caverns/primordial.lua b/df_caverns/primordial.lua
index 8ce5dbc..e32d760 100644
--- a/df_caverns/primordial.lua
+++ b/df_caverns/primordial.lua
@@ -20,6 +20,8 @@ local perlin_wave_primordial = {
 	persist = 0.63
 }
 
+local c_air = minetest.get_content_id("air")
+
 -----------------------------------------------------------------------------------------
 -- Fungal biome
 
@@ -50,7 +52,7 @@ local mushroom_cavern_floor = function(abs_cracks, humidity, vi, area, data, dat
 	local rand = math.random() * math.min(abs_cracks, 1) * humidityfactor
 	if rand < 0.001 then
 		data[vi+ystride] = c_giant_mycelium
-	elseif rand < 0.01 then
+	elseif rand < 0.005 then
 		local schematic = df_primordial_items.get_primordial_mushroom()
 		local rotation = (math.random(1,4)-1)*90
 		mapgen_helper.place_schematic_on_data_if_it_fits(data, data_param2, area, area:position(vi+ystride), schematic, rotation)
@@ -133,6 +135,7 @@ local c_jungle_dirt = minetest.get_content_id("df_primordial_items:dirt_with_jun
 local c_plant_matter = minetest.get_content_id("df_primordial_items:plant_matter")
 local c_packed_roots = minetest.get_content_id("df_primordial_items:packed_roots")
 local c_glowstone = minetest.get_content_id("df_underworld_items:glowstone")
+local c_ivy = minetest.get_content_id("df_primordial_items:jungle_ivy")
 
 local jungle_cavern_floor = function(abs_cracks, humidity, vi, area, data, data_param2)
 	local ystride = area.ystride
@@ -141,13 +144,13 @@ local jungle_cavern_floor = function(abs_cracks, humidity, vi, area, data, data_
 	data[vi] = c_jungle_dirt
 
 	local rand = math.random()
-	if rand < 0.05 * humidityfactor then
+	if rand < 0.025 * humidityfactor then
 		local fern_schematic = df_primordial_items.get_fern_schematic()
 		local rotation = (math.random(1,4)-1)*90
 		mapgen_helper.place_schematic_on_data_if_it_fits(data, data_param2, area, area:position(vi+ystride), fern_schematic, rotation)
-	elseif rand < 0.075 * (1-humidityfactor) then
+	elseif rand < 0.05 * (1-humidityfactor) then
 		df_primordial_items.spawn_jungle_mushroom_vm(vi+ystride, area, data)
-	elseif rand < 0.125 * (1-humidityfactor) then
+	elseif rand < 0.1 * (1-humidityfactor) then
 		df_primordial_items.spawn_jungle_tree_vm(math.random(8,14), vi+ystride, area, data)
 	elseif rand < 0.3 then
 		data[vi+ystride] = jungle_plants[math.random(1,#jungle_plants)]
@@ -157,12 +160,38 @@ end
 local jungle_cavern_ceiling = function(abs_cracks, vi, area, data, data_param2)
 	if abs_cracks < 0.25 then
 		data[vi] = c_glowstone
+	elseif abs_cracks > 0.75 and math.random() < 0.1 then
+		local ystride = area.ystride
+		local index = vi - ystride
+		for i = 1, math.random(16) do
+			if data[index] == c_air then
+				data[index] = c_ivy
+				index = index - ystride
+			else
+				break
+			end
+		end
 	end
 end
 
 local jungle_warren_ceiling = function(abs_cracks, vi, area, data, data_param2)
+	if abs_cracks < 0.1 then
+		data[vi] = c_glowstone
+	end
 end
 
+local jungle_warren_floor = function(abs_cracks, vi, area, data, data_param2)
+	local ystride = area.ystride
+	if abs_cracks < 0.7 then
+		data[vi] = c_jungle_dirt
+		local rand = math.random() * abs_cracks
+		if rand < 0.1 then
+			data[vi+ystride] = jungle_plants[math.random(1,#jungle_plants)]
+		end
+	elseif abs_cracks < 1 then
+		data[vi] = c_dirt
+	end
+end
 ---------------------------------------------------------------------------------------------------------
 
 local decorate_primordial = function(minp, maxp, seed, vm, node_arrays, area, data)
@@ -233,11 +262,11 @@ local decorate_primordial = function(minp, maxp, seed, vm, node_arrays, area, da
 		local abs_cracks = math.abs(cracks)
 		local jungle = nvals_cave[vi] < 0
 		
---		if jungle then
---			jungle_warren_ceiling(abs_cracks, vi, area, data, data_param2)
---		else
+		if jungle then
+			jungle_warren_ceiling(abs_cracks, vi, area, data, data_param2)
+		else
 			mushroom_warren_ceiling(abs_cracks, vi, area, data, data_param2)
---		end
+		end
 
 	end
 
@@ -250,17 +279,21 @@ local decorate_primordial = function(minp, maxp, seed, vm, node_arrays, area, da
 		local abs_cracks = math.abs(cracks)
 		local jungle = nvals_cave[vi] < 0
 		
---		if jungle then
---			jungle_warren_floor(abs_cracks, vi, area, data, data_param2)
---		else
+		if jungle then
+			jungle_warren_floor(abs_cracks, vi, area, data, data_param2)
+		else
 			mushroom_warren_floor(abs_cracks, vi, area, data, data_param2)
---		end
+		end
 	end
 
 	-- columns
+	-- no flowstone below the Sunless Sea, replace with something else
 	for _, vi in ipairs(node_arrays.column_nodes) do
 		local jungle = nvals_cave[vi] < 0
 		if jungle then
+			data[vi] = c_plant_matter
+		else
+			data[vi] = c_mycelial_dirt
 		end
 	end
 
@@ -276,14 +309,14 @@ subterrane.register_layer({
 	perlin_cave = perlin_cave_primordial,
 	perlin_wave = perlin_wave_primordial,
 	solidify_lava = true,
-	columns = {
-		maximum_radius = 20,
-		minimum_radius = 5,
-		node = "df_mapitems:wet_flowstone", --TODO: no flowstone below the Sunless Sea, replace with something else
-		weight = 0.5,
-		maximum_count = 60,
-		minimum_count = 10,
-	},
+--	columns = {
+--		maximum_radius = 20,
+--		minimum_radius = 5,
+--		node = "df_mapitems:wet_flowstone", -- no flowstone below the Sunless Sea, replace with something else
+--		weight = 0.5,
+--		maximum_count = 60,
+--		minimum_count = 10,
+--	},
 	decorate = decorate_primordial,
 	double_frequency = true,
 	is_ground_content = df_caverns.is_ground_content,
diff --git a/df_caverns/shared.lua b/df_caverns/shared.lua
index af6a949..48ab793 100644
--- a/df_caverns/shared.lua
+++ b/df_caverns/shared.lua
@@ -211,7 +211,6 @@ end
 
 ---------------------------------------------------------------------------------
 -- This method allows subterrane to overgenerate caves without destroying any of the decorations
--- Water is included so that the sunless sea won't have gaps torn in it
 local dfcaverns_nodes = nil
 local dfcaverns_mods = {
 	"df_farming:",
diff --git a/df_caverns/underworld.lua b/df_caverns/underworld.lua
index e14aff3..fc6ae65 100644
--- a/df_caverns/underworld.lua
+++ b/df_caverns/underworld.lua
@@ -5,6 +5,7 @@ end
 local bones_loot_path = minetest.get_modpath("bones_loot")
 
 local c_slade = minetest.get_content_id("df_underworld_items:slade")
+local c_slade_block = minetest.get_content_id("df_underworld_items:slade_block")
 local c_air = minetest.get_content_id("air")
 local c_water = minetest.get_content_id("default:water_source")
 
@@ -60,6 +61,9 @@ local y_min = median - 2*wave_mult + floor_displace - 2*floor_mult
 
 --df_caverns.config.underworld_min = y_min
 
+--local poisson = mapgen_helper.get_poisson_points({x=-32000, z=-32000}, {x=32000, z=32000}, 1000)
+--minetest.debug(dump(poisson.objects))
+
 ---------------------------------------------------------
 -- Buildings
 
@@ -207,21 +211,24 @@ local get_corner = function(pos)
 	return {x = math.floor((pos.x+32) / pit_region_size) * pit_region_size - 32, z = math.floor((pos.z+32) / pit_region_size) * pit_region_size - 32}
 end
 
-local mapgen_seed = tonumber(minetest.get_mapgen_setting("seed"))
+local mapgen_seed = tonumber(minetest.get_mapgen_setting("seed")) % 2^21
 
 local get_pit = function(pos)
 	if region_mapblocks < 1 then return nil end
 
 	local corner_xz = get_corner(pos)
-	local next_seed = math.floor(math.random() * 2^31)
+	local next_seed = math.floor(math.random() * 2^21)
 	math.randomseed(corner_xz.x + corner_xz.z * 2 ^ 8 + mapgen_seed)
 	local location = scatter_2d(corner_xz, pit_region_size, radius_pit_max + radius_pit_variance)
 	local variance_multiplier = math.random()
 	local radius = variance_multiplier * (radius_pit_max - 15) + 15
 	local variance = radius_pit_variance/2 + radius_pit_variance*variance_multiplier/2
 	local depth = math.random(plasma_depth_min, plasma_depth_max)
+	
+	local shaft_seed = math.random()
+	local shaft_location = corner_xz
 	math.randomseed(next_seed)
-	return {location = location, radius = radius, variance = variance, depth = depth}
+	return {location = location, radius = radius, variance = variance, depth = depth}, {seed = shaft_seed, location = shaft_location}
 end
 
 local perlin_pit = {
@@ -241,12 +248,14 @@ minetest.register_chatcommand("find_pit", {
 	decription = "find a nearby glowing pit",
 	func = function(name, param)
 		local player = minetest.get_player_by_name(name)
-		local pit = get_pit(player:get_pos())
-		minetest.chat_send_player(name, "Pit location: x=" .. math.floor(pit.location.x) .. " z=" .. math.floor(pit.location.z))
+		local pit, shaft = get_pit(player:get_pos())
+		if pit then
+			minetest.chat_send_player(name, "Pit location: x=" .. math.floor(pit.location.x) .. " z=" .. math.floor(pit.location.z))
+			minetest.chat_send_player(name, "Shaft location: x=" .. math.floor(shaft.location.x) .. " z=" .. math.floor(shaft.location.z))
+		end
 	end,
 })
 
-
 minetest.register_on_generated(function(minp, maxp, seed)
 
 	--if out of range of cave definition limits, abort
@@ -264,9 +273,9 @@ minetest.register_on_generated(function(minp, maxp, seed)
 	local nvals_wave = mapgen_helper.perlin2d("df_caverns:underworld_wave", emin, emax, perlin_wave) --cave noise for structure
 	local nvals_zone = mapgen_helper.perlin2d("df_caverns:underworld_zone", emin, emax, perlin_zone) --building zones
 	
-	local pit = get_pit(minp)
+	local pit, shaft = get_pit(minp)
 	--minetest.chat_send_all(minetest.pos_to_string(pit.location))
-	
+
 	local buildings = get_buildings(emin, emax, nvals_zone)
 	
 	local pit_uninitialized = true
@@ -279,8 +288,9 @@ minetest.register_on_generated(function(minp, maxp, seed)
 			local wave = nvals_wave[index2d] * wave_mult
 			
 			local floor_height =  math.floor(abs_cave * floor_mult + median + floor_displace + wave)
+			local underside_height = y_min + math.abs(wave) / 5
 			local ceiling_height =  math.floor(abs_cave * ceiling_mult + median + ceiling_displace + wave)
-			if y < floor_height and y > y_min + math.abs(wave) / 5 then -- divide wave by five to smooth out the underside of the slade, we only want the interface to ripple a little down here
+			if y < floor_height and y > underside_height then -- divide wave by five to smooth out the underside of the slade, we only want the interface to ripple a little down here
 				data[vi] = c_slade
 				if	pit and
 					pit.location.x - radius_pit_max - radius_pit_variance < maxp.x and
@@ -388,6 +398,50 @@ minetest.register_on_generated(function(minp, maxp, seed)
 			end
 		end
 	end
+	
+	-- puzzle shaft
+	local puzzle_init = nil	
+	if pit_uninitialized and minp.x == shaft.location.x and minp.z == shaft.location.z then
+		local index2d = mapgen_helper.index2d(emin, emax, minp.x + 3, minp.z + 3)
+		local abs_cave = math.abs(nvals_cave[index2d]) -- range is from 0 to approximately 2, with 0 being connected and 2s being islands
+		local wave = nvals_wave[index2d] * wave_mult
+			
+		local floor_height =  math.floor(abs_cave * floor_mult + median + floor_displace + wave)
+		local underside_height = math.floor(y_min + math.abs(wave) / 5)
+		
+		local shaftwallmin = {x=minp.x, y=math.max(underside_height-3, minp.y), z=minp.z}
+		local shaftwallmax = {x=minp.x+4, y=math.min(floor_height, maxp.y), z=minp.z+4}
+		local shaftcoremin = {x=minp.x+1, y=shaftwallmin.y, z=minp.z+1}
+		local shaftcoremax = {x=minp.x+3, y=math.min(floor_height+3, maxp.y), z=minp.z+3}
+
+		minetest.debug("minp,maxp")
+		minetest.debug(minetest.pos_to_string(minp))
+		minetest.debug(minetest.pos_to_string(maxp))
+
+		minetest.debug("wall")
+		minetest.debug(minetest.pos_to_string(shaftwallmin))
+		minetest.debug(minetest.pos_to_string(shaftwallmax))
+	
+		for wall_vi in area:iterp(shaftwallmin, shaftwallmax) do
+			data[wall_vi] = c_slade_block
+		end
+
+		minetest.debug("core")
+		minetest.debug(minetest.pos_to_string(shaftcoremin))
+		minetest.debug(minetest.pos_to_string(shaftcoremax))
+
+		for core_vi in area:iterp(shaftcoremin, shaftcoremax) do
+			data[core_vi] = c_air
+		end
+		
+		local puzzle_seal_y = floor_height-1--math.floor((floor_height+underside_height)/2)
+		if puzzle_seal_y < maxp.y and puzzle_seal_y > minp.y then
+			for seal_vi in area:iter(minp.x+1, puzzle_seal_y, minp.z+1, minp.x+3, puzzle_seal_y, minp.z+3) do
+				data[seal_vi] = c_slade_block
+			end			
+			puzzle_init = {x=minp.x+2, y=puzzle_seal_y, z=minp.z+2}
+		end
+	end
 
 	--send data back to voxelmanip
 	vm:set_data(data)
@@ -399,6 +453,9 @@ minetest.register_on_generated(function(minp, maxp, seed)
 	--write it to world
 	vm:write_to_map()
 	
+	if puzzle_init ~= nil then
+	end
+	
 	if bones_loot_path then
 		for i = 1, 30 do
 			local x = math.random(minp.x, maxp.x)
diff --git a/df_primordial_items/depends.txt b/df_primordial_items/depends.txt
deleted file mode 100644
index 5473e9f..0000000
--- a/df_primordial_items/depends.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-default
-mapgen_helper
-subterrane
-df_underworld_items
\ No newline at end of file
diff --git a/df_primordial_items/fungal_nodes.lua b/df_primordial_items/fungal_nodes.lua
index 5b77131..9e2220a 100644
--- a/df_primordial_items/fungal_nodes.lua
+++ b/df_primordial_items/fungal_nodes.lua
@@ -26,7 +26,7 @@ minetest.register_node("df_primordial_items:fungal_grass_1", {
 })
 
 minetest.register_node("df_primordial_items:fungal_grass_2", {
-	description = S("Primordial Jungle Grass"),
+	description = S("Primordial Fungal Grass"),
 	_doc_items_longdesc = df_primordial_items.doc.fungal_grass_desc,
 	_doc_items_usagehelp = df_primordial_items.doc.fungal_grass_usage,
 	tiles = {"dfcaverns_mush_grass_02.png"},
diff --git a/df_primordial_items/giant_mycelium.lua b/df_primordial_items/giant_mycelium.lua
index 596b11f..03f5c31 100644
--- a/df_primordial_items/giant_mycelium.lua
+++ b/df_primordial_items/giant_mycelium.lua
@@ -33,7 +33,7 @@ minetest.register_node("df_primordial_items:giant_hypha_root", {
 	light_source = 2,
 	is_ground_content = false,
 	groups = {oddly_breakable_by_hand = 1, choppy = 2, hypha = 1},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	drop = {
 		max_items = 1,
 		items = {
@@ -60,7 +60,7 @@ minetest.register_node("df_primordial_items:giant_hypha", {
 	light_source = 2,
 	is_ground_content = false,
 	groups = {oddly_breakable_by_hand = 1, choppy = 2, hypha = 1},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	drop = {
 		max_items = 1,
 		items = {
@@ -300,7 +300,7 @@ minetest.register_node("df_primordial_items:giant_hypha_apical_meristem", {
 	is_ground_content = false,
 	groups = {oddly_breakable_by_hand = 1, choppy = 2, hypha = 1, light_sensitive_fungus = 13},
 	_dfcaverns_dead_node = "df_primordial_items:giant_hypha_root",
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_construct = function(pos)
 		minetest.get_node_timer(pos):start(math.random(min_growth_delay, max_growth_delay))
 	end,
@@ -362,7 +362,7 @@ minetest.register_node("df_primordial_items:giant_hypha_apical_mapgen", {
 
 	is_ground_content = false,
 	groups = {oddly_breakable_by_hand = 1, choppy = 2, hypha = 1, not_in_creative_inventory = 1},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 })
 
 local grow_mycelium_immediately = function(pos)
diff --git a/df_primordial_items/jungle_mushroom.lua b/df_primordial_items/jungle_mushroom.lua
index 5006c57..57cc7ed 100644
--- a/df_primordial_items/jungle_mushroom.lua
+++ b/df_primordial_items/jungle_mushroom.lua
@@ -13,7 +13,7 @@ minetest.register_node("df_primordial_items:jungle_mushroom_trunk", {
 	paramtype2 = "facedir",
 	is_ground_content = false,
 	groups = {tree = 1, choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_place = minetest.rotate_node
 })
 
@@ -25,7 +25,7 @@ minetest.register_node("df_primordial_items:jungle_mushroom_cap_1", {
 	paramtype2 = "facedir",
 	is_ground_content = false,
 	groups = {tree = 1, choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_place = minetest.rotate_node,
 	drop = {
 		max_items = 1,
@@ -49,7 +49,7 @@ minetest.register_node("df_primordial_items:jungle_mushroom_cap_2", {
 	paramtype2 = "facedir",
 	is_ground_content = false,
 	groups = {tree = 1, choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_place = minetest.rotate_node,
 	drop = {
 		max_items = 1,
diff --git a/df_primordial_items/jungle_nodes.lua b/df_primordial_items/jungle_nodes.lua
index ff5a001..f9ca8cd 100644
--- a/df_primordial_items/jungle_nodes.lua
+++ b/df_primordial_items/jungle_nodes.lua
@@ -174,19 +174,21 @@ minetest.register_node("df_primordial_items:jungle_ivy", {
 	tiles = {"dfcaverns_jungle_ivy_01.png"},
 	inventory_image = "dfcaverns_jungle_ivy_01.png",
 	wield_image = "dfcaverns_jungle_ivy_01.png",
-	groups = {snappy = 3, flora = 1, attached_node = 1, flammable = 1},
+	groups = {snappy = 3, flora = 1, flammable = 1},
 	paramtype = "light",
-	paramtype2 = "wallmounted",
-	drawtype = "signlike",
+	drawtype = "plantlike",
+	place_param2 = 3,
+	--paramtype2 = "wallmouinted",
+	--drawtype = "signlike",
 	sounds = default.node_sound_leaves_defaults(),
 	use_texture_alpha = true,
 	sunlight_propagates = true,
 	is_ground_content = false,
 	walkable = false,
 	climbable = true,
-	selection_box = {
-		type = "wallmounted",
-	},
+--	selection_box = {
+--		type = "wallmounted",
+--	},
 })
 
 -------------------------------------------------------------------------------------
@@ -259,6 +261,18 @@ minetest.register_node("df_primordial_items:packed_roots", {
 	sounds = default.node_sound_wood_defaults(),
 })
 
+minetest.register_abm({
+	label = "Plant matter converting to roots",
+	nodenames = {"df_primordial_items:plant_matter"},
+	interval = 10.0,
+	chance = 5,
+	action = function(pos, node, active_object_count, active_object_count_wider)
+		if minetest.find_node_near(pos, 1, {"air"}) == nil then
+			minetest.set_node(pos, {name="df_primordial_items:packed_roots"})
+		end
+	end
+})
+
 ----------------------------------------------------------------------------------------
 -- Roots
 
diff --git a/df_primordial_items/jungle_tree.lua b/df_primordial_items/jungle_tree.lua
index 8eb1197..0128bd9 100644
--- a/df_primordial_items/jungle_tree.lua
+++ b/df_primordial_items/jungle_tree.lua
@@ -10,6 +10,7 @@ minetest.register_node("df_primordial_items:jungle_leaves", {
 	drawtype = "plantlike",
 	walkable = false,
 	waving = 2,
+	visual_scale = 1.2,
 	tiles = {"dfcaverns_jungle_leaves_01.png"},
 	inventory_image = "dfcaverns_jungle_leaves_01.png",
 	wield_image = "dfcaverns_jungle_leaves_01.png",
@@ -40,6 +41,7 @@ minetest.register_node("df_primordial_items:jungle_leaves_glowing", {
 	drawtype = "plantlike",
 	walkable = false,
 	waving = 2,
+	visual_scale = 1.2,
 	tiles = {"dfcaverns_jungle_leaves_02.png"},
 	inventory_image = "dfcaverns_jungle_leaves_02.png",
 	wield_image = "dfcaverns_jungle_leaves_02.png",
diff --git a/df_primordial_items/mod.conf b/df_primordial_items/mod.conf
index 194ff3d..a9ad26e 100644
--- a/df_primordial_items/mod.conf
+++ b/df_primordial_items/mod.conf
@@ -1,3 +1,3 @@
 name = df_primordial_items
 description = A collection of flora found in the "primordial" cavern layer of DF Caverns
-depends = default, mapgen_helper, subterrane
\ No newline at end of file
+depends = default, mapgen_helper, subterrane, df_underworld_items, df_trees
\ No newline at end of file
diff --git a/df_primordial_items/primordial_mushroom.lua b/df_primordial_items/primordial_mushroom.lua
index 5941be1..5597c15 100644
--- a/df_primordial_items/primordial_mushroom.lua
+++ b/df_primordial_items/primordial_mushroom.lua
@@ -10,7 +10,7 @@ minetest.register_node("df_primordial_items:mushroom_trunk", {
 	paramtype2 = "facedir",
 	is_ground_content = false,
 	groups = {tree = 1, choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_place = minetest.rotate_node
 })
 
@@ -22,7 +22,7 @@ minetest.register_node("df_primordial_items:mushroom_cap", {
 	paramtype2 = "facedir",
 	is_ground_content = false,
 	groups = {tree = 1, choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
-	sounds = default.node_sound_wood_defaults(),
+	sounds = df_trees.node_sound_tree_soft_fungus_defaults(),
 	on_place = minetest.rotate_node
 })
 
diff --git a/df_trees/tunnel_tube.lua b/df_trees/tunnel_tube.lua
index 29dafd7..b2e5e93 100644
--- a/df_trees/tunnel_tube.lua
+++ b/df_trees/tunnel_tube.lua
@@ -393,6 +393,10 @@ df_trees.spawn_tunnel_tube_vm = function(vi, area, data, param2_data, height, di
 
 	local previous_vi = vi
 	local pattern = tunnel_tube_patterns[height]
+	if pattern == nil then
+		minetest.log("error", "Tunnel tube pattern was nil somehow. height: " .. string(height) .. " location: " .. minetest.pos_to_string(area:position(vi)))
+		return nil
+	end
 	for i, nodepattern in ipairs(pattern) do
 		local current_vi = vi + nodepattern[1] * increment
 		if data[current_vi] == c_air or data[current_vi] == c_ignore then