diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 0b3d5daa6..a3bb64818 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -2461,6 +2461,8 @@ These functions return the leftover itemstack.
     * Map of Lua entities, indexed by active object id
 * `minetest.registered_ores`
     * List of registered ore definitions.
+* `minetest.registered_biomes`
+    * List of registered biome definitions.
 * `minetest.registered_decorations`
     * List of registered decoration definitions.
 
diff --git a/games/minimal/mods/default/mapgen.lua b/games/minimal/mods/default/mapgen.lua
index e13dcfaf4..65b67dae5 100644
--- a/games/minimal/mods/default/mapgen.lua
+++ b/games/minimal/mods/default/mapgen.lua
@@ -3,7 +3,6 @@
 --
 
 
-minetest.register_alias("mapgen_air", "air")
 minetest.register_alias("mapgen_stone", "default:stone")
 minetest.register_alias("mapgen_dirt", "default:dirt")
 minetest.register_alias("mapgen_dirt_with_grass", "default:dirt_with_grass")
diff --git a/src/cavegen.cpp b/src/cavegen.cpp
index e1516af08..b8abfbca5 100644
--- a/src/cavegen.cpp
+++ b/src/cavegen.cpp
@@ -43,6 +43,9 @@ CaveV5::CaveV5(Mapgen *mg, PseudoRandom *ps)
 	c_ice                = ndef->getId("mapgen_ice");
 	this->np_caveliquids = &nparams_caveliquids;
 	this->ystride        = mg->csize.X;
+ 
+	if (c_ice == CONTENT_IGNORE)
+		c_ice = CONTENT_AIR;
 
 	dswitchint = ps->range(1, 14);
 	flooded    = ps->range(1, 2) == 2;
diff --git a/src/dungeongen.cpp b/src/dungeongen.cpp
index cb5ea97b6..ce92319e6 100644
--- a/src/dungeongen.cpp
+++ b/src/dungeongen.cpp
@@ -68,6 +68,8 @@ DungeonGen::DungeonGen(Mapgen *mapgen, DungeonParams *dparams)
 
 	// For mapgens using river water
 	dp.c_river_water = mg->ndef->getId("mapgen_river_water_source");
+	if (dp.c_river_water == CONTENT_IGNORE)
+		dp.c_river_water = mg->ndef->getId("mapgen_water_source");
 }
 
 
diff --git a/src/mapgen_v5.cpp b/src/mapgen_v5.cpp
index 92cf00202..48b717292 100644
--- a/src/mapgen_v5.cpp
+++ b/src/mapgen_v5.cpp
@@ -38,7 +38,6 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "mg_ore.h"
 #include "mg_decoration.h"
 #include "mapgen_v5.h"
-#include "util/directiontables.h"
 
 
 FlagDesc flagdesc_mapgen_v5[] = {
@@ -216,9 +215,9 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 		data->blockpos_requested.Y <= data->blockpos_max.Y &&
 		data->blockpos_requested.Z <= data->blockpos_max.Z);
 
-	generating = true;
-	vm   = data->vmanip;
-	ndef = data->nodedef;
+	this->generating = true;
+	this->vm   = data->vmanip;
+	this->ndef = data->nodedef;
 	//TimeTaker t("makeChunk");
 
 	v3s16 blockpos_min = data->blockpos_min;
diff --git a/src/mapgen_v6.cpp b/src/mapgen_v6.cpp
index 0a9f80dc9..57d0f59b3 100644
--- a/src/mapgen_v6.cpp
+++ b/src/mapgen_v6.cpp
@@ -17,6 +17,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
+
 #include "mapgen.h"
 #include "voxel.h"
 #include "noise.h"
@@ -37,6 +38,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "mg_decoration.h"
 #include "mapgen_v6.h"
 
+
 FlagDesc flagdesc_mapgen_v6[] = {
 	{"jungles",    MGV6_JUNGLES},
 	{"biomeblend", MGV6_BIOMEBLEND},
@@ -47,7 +49,8 @@ FlagDesc flagdesc_mapgen_v6[] = {
 	{NULL,         0}
 };
 
-///////////////////////////////////////////////////////////////////////////////
+
+/////////////////////////////////////////////////////////////////////////////
 
 
 MapgenV6::MapgenV6(int mapgenid, MapgenParams *params, EmergeManager *emerge)
@@ -197,7 +200,6 @@ void MapgenV6Params::writeParams(Settings *settings) const
 
 //////////////////////// Some helper functions for the map generator
 
-
 // Returns Y one under area minimum if not found
 s16 MapgenV6::find_stone_level(v2s16 p2d)
 {
@@ -468,11 +470,11 @@ void MapgenV6::makeChunk(BlockMakeData *data)
 	assert(data->vmanip);
 	assert(data->nodedef);
 	assert(data->blockpos_requested.X >= data->blockpos_min.X &&
-		   data->blockpos_requested.Y >= data->blockpos_min.Y &&
-		   data->blockpos_requested.Z >= data->blockpos_min.Z);
+		data->blockpos_requested.Y >= data->blockpos_min.Y &&
+		data->blockpos_requested.Z >= data->blockpos_min.Z);
 	assert(data->blockpos_requested.X <= data->blockpos_max.X &&
-		   data->blockpos_requested.Y <= data->blockpos_max.Y &&
-		   data->blockpos_requested.Z <= data->blockpos_max.Z);
+		data->blockpos_requested.Y <= data->blockpos_max.Y &&
+		data->blockpos_requested.Z <= data->blockpos_max.Z);
 
 	this->generating = true;
 	this->vm   = data->vmanip;
@@ -808,7 +810,7 @@ void MapgenV6::flowMud(s16 &mudflow_minpos, s16 &mudflow_maxpos)
 					continue;
 
 				// Drop mud on side
-				for(u32 di = 0; di < 4; di++) {
+				for (u32 di = 0; di < 4; di++) {
 					v3s16 dirp = dirs4[di];
 					u32 i2 = i;
 					// Move to side
@@ -833,7 +835,7 @@ void MapgenV6::flowMud(s16 &mudflow_minpos, s16 &mudflow_maxpos)
 						vm->m_area.add_y(em, i2, -1);
 						n2 = &vm->m_data[i2];
 						// if out of known area
-						if(vm->m_area.contains(i2) == false ||
+						if (vm->m_area.contains(i2) == false ||
 								n2->getContent() == CONTENT_IGNORE) {
 							dropped_to_unknown = true;
 							break;
@@ -848,7 +850,7 @@ void MapgenV6::flowMud(s16 &mudflow_minpos, s16 &mudflow_maxpos)
 					if (!dropped_to_unknown) {
 						*n2 = *n;
 						// Set old place to be air (or water)
-						if(old_is_water)
+						if (old_is_water)
 							*n = MapNode(c_water_source);
 						else
 							*n = MapNode(CONTENT_AIR);
diff --git a/src/mapgen_v7.cpp b/src/mapgen_v7.cpp
index 3842b1a96..50559f9a5 100644
--- a/src/mapgen_v7.cpp
+++ b/src/mapgen_v7.cpp
@@ -46,6 +46,7 @@ FlagDesc flagdesc_mapgen_v7[] = {
 	{NULL,        0}
 };
 
+
 ///////////////////////////////////////////////////////////////////////////////