diff --git a/src/MinedMap.cpp b/src/MinedMap.cpp
index 885ecc2..6fe1383 100644
--- a/src/MinedMap.cpp
+++ b/src/MinedMap.cpp
@@ -113,10 +113,16 @@ static Resource::Color collectColors(size_t x, size_t z, const World::Block &blo
 		uint8_t biome = e.first;
 		size_t count = e.second;
 
+		if (biome == 0xff)
+			continue;
+
 		c = c + count * block.getColor(biome);
 		total += count;
 	}
 
+	if (!total)
+		return block.getColor(0);
+
 	return (1.0f / total) * c;
 }
 
@@ -255,7 +261,7 @@ static void makeBiome(const std::string &regiondir, const std::string &outputdir
 
 	try {
 		std::unique_ptr<uint8_t[]> biomemap(new uint8_t[DIM*DIM]);
-		std::memset(biomemap.get(), 0, DIM*DIM);
+		std::memset(biomemap.get(), 0xff, DIM*DIM);
 
 		World::Region::visitChunks(input.c_str(), [&] (size_t X, size_t Z, const World::ChunkData *chunk) {
 			addChunkBiome(biomemap.get(), X, Z, chunk);
diff --git a/src/World/Chunk.cpp b/src/World/Chunk.cpp
index 161dc70..423d7e8 100644
--- a/src/World/Chunk.cpp
+++ b/src/World/Chunk.cpp
@@ -78,7 +78,7 @@ uint8_t Chunk::getBiome(size_t x, size_t y, size_t z) const {
 	else if (biomeBytes)
 		return biomeBytes->getValue(z*SIZE + x);
 	else
-		return 0;
+		return 0xff;
 }
 
 Block Chunk::getBlock(size_t x, Chunk::Height height, size_t z) const {