diff --git a/README.md b/README.md
index 9481384..edf300f 100644
--- a/README.md
+++ b/README.md
@@ -74,4 +74,7 @@ SOFTWARE.
  * `nether_rack`* (files starting with "nether_rack"): Zeg9
  * `nether_tool_`* (files starting with "nether_tool_"): color adjusted versions from "[default](https://github.com/minetest/minetest_game/tree/master/mods/default)" mod, originals by BlockMen
 
-All other media: Copyright © 2013 PilzAdam, licensed under CC BY-SA 3.0 by PilzAdam.
\ No newline at end of file
+### [Unlicensed but permission for inclusion by kovaszos_uborka](https://www.planetminecraft.com/member/kovaszos_uborka/)
+ * `nether_brick_deep.png` (edited by TenPlus1)
+
+All other media: Copyright © 2013 PilzAdam, licensed under CC BY-SA 3.0 by PilzAdam.
diff --git a/crafts.lua b/crafts.lua
index f880e19..88d1d07 100644
--- a/crafts.lua
+++ b/crafts.lua
@@ -44,6 +44,14 @@ minetest.register_craft({
 	}
 })
 
+minetest.register_craft({
+	output = "nether:brick_deep 4",
+	recipe = {
+		{"nether:rack_deep", "nether:rack_deep"},
+		{"nether:rack_deep", "nether:rack_deep"}
+	}
+})
+
 minetest.register_craft({
     output = "nether:basalt_hewn",
     type = "shapeless",
@@ -61,4 +69,4 @@ minetest.register_craft({
   }
 })
 
--- See tools.lua for tools related crafting
\ No newline at end of file
+-- See tools.lua for tools related crafting
diff --git a/nodes.lua b/nodes.lua
index 3205783..104b5ff 100644
--- a/nodes.lua
+++ b/nodes.lua
@@ -161,6 +161,13 @@ minetest.register_node("nether:fence_nether_brick", {
 	sounds = default.node_sound_stone_defaults(),
 })
 
+minetest.register_node("nether:brick_deep", {
+	description = S("Deep Nether Brick"),
+	tiles = {"nether_brick_deep.png"},
+	is_ground_content = false,
+	groups = {cracky = 2, level = 2},
+	sounds = default.node_sound_stone_defaults()
+})
 
 -- Register stair and slab
 
diff --git a/portal_api.lua b/portal_api.lua
index bec8e0f..951ed5d 100644
--- a/portal_api.lua
+++ b/portal_api.lua
@@ -2216,7 +2216,7 @@ function nether.volume_is_natural_and_unprotected(minp, maxp, player_name)
 			if id ~= c_air and id ~= c_ignore and id ~= nil then -- checked for common natural or not emerged
 				local name = minetest.get_name_from_content_id(id)
 				local nodedef = minetest.registered_nodes[name]
-				if not nodedef.is_ground_content then
+				if nodedef and not nodedef.is_ground_content then
 					-- trees are natural but not "ground content"
 					local node_groups = nodedef.groups
 					if node_groups == nil or (node_groups.tree == nil and node_groups.leaves == nil and node_groups.leafdecay == nil) then
diff --git a/textures/nether_brick_deep.png b/textures/nether_brick_deep.png
new file mode 100644
index 0000000..a11e53e
Binary files /dev/null and b/textures/nether_brick_deep.png differ