diff --git a/src/mapgen.cpp b/src/mapgen.cpp
index 66892a574..576fb219a 100644
--- a/src/mapgen.cpp
+++ b/src/mapgen.cpp
@@ -524,6 +524,10 @@ MapgenBasic::~MapgenBasic()
 
 MgStoneType MapgenBasic::generateBiomes()
 {
+	// can't generate biomes without a biome generator!
+	assert(biomegen);
+	assert(biomemap);
+
 	v3s16 em = vm->m_area.getExtent();
 	u32 index = 0;
 	MgStoneType stone_type = MGSTONE_STONE;
@@ -546,6 +550,8 @@ MgStoneType MapgenBasic::generateBiomes()
 		bool river_water_above = c_above == c_river_water_source;
 		bool water_above = c_above == c_water_source || river_water_above;
 
+		biomemap[index] = BIOME_NONE;
+
 		// If there is air or water above enable top/filler placement, otherwise force
 		// nplaced to stone level by setting a number exceeding any possible filler depth.
 		u16 nplaced = (air_above || water_above) ? 0 : U16_MAX;
@@ -560,11 +566,19 @@ MgStoneType MapgenBasic::generateBiomes()
 			// 1. At the surface of stone below air or water.
 			// 2. At the surface of water below air.
 			// 3. When stone or water is detected but biome has not yet been calculated.
-			if ((c == c_stone && (air_above || water_above || !biome))
-					|| ((c == c_water_source || c == c_river_water_source)
-						&& (air_above || !biome))) {
+			bool is_stone_surface = (c == c_stone) &&
+				(air_above || water_above || !biome);
+
+			bool is_water_surface =
+				(c == c_water_source || c == c_river_water_source) &&
+				(air_above || !biome);
+
+			if (is_stone_surface || is_water_surface) {
 				biome = biomegen->getBiomeAtIndex(index, y);
 
+				if (biomemap[index] == BIOME_NONE && is_stone_surface)
+					biomemap[index] = biome->index;
+
 				depth_top = biome->depth_top;
 				base_filler = MYMAX(depth_top +
 					biome->depth_filler +
diff --git a/src/mapgen_flat.cpp b/src/mapgen_flat.cpp
index 724f06825..7cc6aad5c 100644
--- a/src/mapgen_flat.cpp
+++ b/src/mapgen_flat.cpp
@@ -192,7 +192,6 @@ void MapgenFlat::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	biomegen->getBiomes(heightmap);
 	MgStoneType stone_type = generateBiomes();
 
 	if (flags & MG_CAVES)
diff --git a/src/mapgen_fractal.cpp b/src/mapgen_fractal.cpp
index b613bf358..c47a7bfdc 100644
--- a/src/mapgen_fractal.cpp
+++ b/src/mapgen_fractal.cpp
@@ -208,7 +208,6 @@ void MapgenFractal::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	biomegen->getBiomes(heightmap);
 	MgStoneType stone_type = generateBiomes();
 
 	if (flags & MG_CAVES)
diff --git a/src/mapgen_v5.cpp b/src/mapgen_v5.cpp
index 3e10ec2a5..74d5e1ee3 100644
--- a/src/mapgen_v5.cpp
+++ b/src/mapgen_v5.cpp
@@ -190,7 +190,6 @@ void MapgenV5::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	biomegen->getBiomes(heightmap);
 	MgStoneType stone_type = generateBiomes();
 
 	// Generate caves
diff --git a/src/mapgen_v7.cpp b/src/mapgen_v7.cpp
index 7327facae..35dcdcd94 100644
--- a/src/mapgen_v7.cpp
+++ b/src/mapgen_v7.cpp
@@ -219,7 +219,6 @@ void MapgenV7::makeChunk(BlockMakeData *data)
 
 	// Init biome generator, place biome-specific nodes, and build biomemap
 	biomegen->calcBiomeNoise(node_min);
-	biomegen->getBiomes(heightmap);
 	MgStoneType stone_type = generateBiomes();
 
 	if (flags & MG_CAVES)
diff --git a/src/mapgen_valleys.cpp b/src/mapgen_valleys.cpp
index 6581b792f..bbf20719d 100644
--- a/src/mapgen_valleys.cpp
+++ b/src/mapgen_valleys.cpp
@@ -250,10 +250,7 @@ void MapgenValleys::makeChunk(BlockMakeData *data)
 	// Generate base terrain with initial heightmaps
 	s16 stone_surface_max_y = generateTerrain();
 
-	// Build biomemap
-	m_bgen->getBiomes(heightmap);
-
-	// Place biome-specific nodes
+	// Place biome-specific nodes and build biomemap
 	MgStoneType stone_type = generateBiomes();
 
 	// Cave creation.