diff --git a/src/main/java/de/bixilon/minosoft/data/mappings/tweaker/VersionTweaker.kt b/src/main/java/de/bixilon/minosoft/data/mappings/tweaker/VersionTweaker.kt
index ce491ffb7..a033ebb0a 100644
--- a/src/main/java/de/bixilon/minosoft/data/mappings/tweaker/VersionTweaker.kt
+++ b/src/main/java/de/bixilon/minosoft/data/mappings/tweaker/VersionTweaker.kt
@@ -93,7 +93,11 @@ object VersionTweaker {
             return
         }
         for ((sectionHeight, section) in sections) {
-            for ((location, blockInfo) in section.blocks) {
+            for ((index, blockInfo) in section.blocks.withIndex()) {
+                if (blockInfo == null) {
+                    continue
+                }
+                val location = ChunkSection.getPosition(index)
                 val newBlock = transformBlock(blockInfo.block, sections, location, sectionHeight)
                 if (newBlock === blockInfo.block) {
                     continue
diff --git a/src/main/java/de/bixilon/minosoft/data/world/Chunk.kt b/src/main/java/de/bixilon/minosoft/data/world/Chunk.kt
index 2e73849e6..8ce2a51e5 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/Chunk.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/Chunk.kt
@@ -56,7 +56,7 @@ class Chunk(
                 }
                 // replace all chunk sections
                 for ((sectionHeight, chunkSection) in it) {
-                    getSectionOrCreate(sectionHeight).setData(chunkSection, merge)
+                    getSectionOrCreate(sectionHeight).setData(chunkSection)
                 }
             }
             data.biomeAccessor?.let {
@@ -82,7 +82,7 @@ class Chunk(
         getSectionOrCreate(position.getSectionHeight()).let {
             val inChunkSectionLocation = position.getInChunkSectionLocation()
             if (block == null) {
-                it.blocks.remove(inChunkSectionLocation)
+                it.blocks[ChunkSection.getIndex(inChunkSectionLocation)] = null
                 return
             }
             it.setBlockInfo(inChunkSectionLocation, BlockInfo(block))
diff --git a/src/main/java/de/bixilon/minosoft/data/world/ChunkSection.kt b/src/main/java/de/bixilon/minosoft/data/world/ChunkSection.kt
index ef7754fe7..767480723 100644
--- a/src/main/java/de/bixilon/minosoft/data/world/ChunkSection.kt
+++ b/src/main/java/de/bixilon/minosoft/data/world/ChunkSection.kt
@@ -13,24 +13,21 @@
 package de.bixilon.minosoft.data.world
 
 import de.bixilon.minosoft.data.mappings.blocks.BlockState
+import de.bixilon.minosoft.protocol.protocol.ProtocolDefinition
 
 /**
  * Collection of 16x16x16 blocks
  */
-class ChunkSection constructor(
-    val blocks: MutableMap<InChunkSectionPosition, BlockInfo> = mutableMapOf(),
+class ChunkSection(
+    val blocks: Array<BlockInfo?> = arrayOfNulls(ProtocolDefinition.BLOCKS_PER_SECTION),
 ) {
 
     fun getBlockInfo(position: InChunkSectionPosition): BlockInfo? {
-        return blocks[position]
+        return blocks[getIndex(position)]
     }
 
     fun setBlockInfo(position: InChunkSectionPosition, blockInfo: BlockInfo?) {
-        if (blockInfo == null) {
-            blocks.remove(position)
-            return
-        }
-        blocks[position] = blockInfo
+        blocks[getIndex(position)] = blockInfo
     }
 
     fun getBlockInfo(x: Int, y: Int, z: Int): BlockInfo? {
@@ -45,10 +42,23 @@ class ChunkSection constructor(
         setBlockInfo(position, BlockInfo(block))
     }
 
-    fun setData(chunkSection: ChunkSection, merge: Boolean = false) {
-        if (!merge) {
-            this.blocks.clear()
+    fun setData(chunkSection: ChunkSection) {
+        for ((index, blockInfo) in chunkSection.blocks.withIndex()) {
+            blocks[index] = blockInfo
+        }
+    }
+
+    companion object {
+        fun getIndex(position: InChunkSectionPosition): Int {
+            return getIndex(position.x, position.y, position.z)
+        }
+
+        fun getIndex(x: Int, y: Int, z: Int): Int {
+            return y shl 8 or (z shl 4) or x
+        }
+
+        fun getPosition(index: Int): InChunkSectionPosition {
+            return InChunkSectionPosition(index and 0x0F, (index shr 8) and 0x0F, (index shr 4) and 0x0F)
         }
-        this.blocks.putAll(chunkSection.blocks)
     }
 }
diff --git a/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/WorldRenderer.kt b/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/WorldRenderer.kt
index 0209c6987..7a9ae8ccb 100644
--- a/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/WorldRenderer.kt
+++ b/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/WorldRenderer.kt
@@ -58,8 +58,11 @@ class WorldRenderer(
 
         val mesh = ChunkMesh()
 
-        for ((position, blockInfo) in section.blocks) {
-            val blockPosition = BlockPosition(chunkPosition, sectionHeight, position)
+        for ((index, blockInfo) in section.blocks.withIndex()) {
+            if (blockInfo == null) {
+                continue
+            }
+            val blockPosition = BlockPosition(chunkPosition, sectionHeight, ChunkSection.getPosition(index))
 
             val neighborBlocks: Array<BlockInfo?> = arrayOfNulls(Directions.DIRECTIONS.size)
             for (direction in Directions.DIRECTIONS) {
diff --git a/src/main/java/de/bixilon/minosoft/util/chunk/ChunkUtil.java b/src/main/java/de/bixilon/minosoft/util/chunk/ChunkUtil.java
index 94c36a72d..4b325e8f7 100644
--- a/src/main/java/de/bixilon/minosoft/util/chunk/ChunkUtil.java
+++ b/src/main/java/de/bixilon/minosoft/util/chunk/ChunkUtil.java
@@ -19,7 +19,6 @@ import de.bixilon.minosoft.data.mappings.blocks.BlockState;
 import de.bixilon.minosoft.data.world.BlockInfo;
 import de.bixilon.minosoft.data.world.ChunkData;
 import de.bixilon.minosoft.data.world.ChunkSection;
-import de.bixilon.minosoft.data.world.InChunkSectionPosition;
 import de.bixilon.minosoft.data.world.biome.DummyBiomeAccessor;
 import de.bixilon.minosoft.data.world.biome.XZBiomeAccessor;
 import de.bixilon.minosoft.data.world.light.DummyLightAccessor;
@@ -62,7 +61,7 @@ public final class ChunkUtil {
             HashMap<Integer, ChunkSection> sectionMap = new HashMap<>();
             for (int sectionHeight = dimension.getLowestSection(); sectionHeight < dimension.getHighestSection(); sectionHeight++) { // max sections per chunks in chunk column
                 if (BitByte.isBitSet(sectionBitMasks[0], sectionHeight)) {
-                    HashMap<InChunkSectionPosition, BlockInfo> blockMap = new HashMap<>();
+                    BlockInfo[] blocks = new BlockInfo[ProtocolDefinition.BLOCKS_PER_SECTION];
 
                     for (int nibbleY = 0; nibbleY < ProtocolDefinition.SECTION_HEIGHT_Y; nibbleY++) {
                         for (int nibbleZ = 0; nibbleZ < ProtocolDefinition.SECTION_WIDTH_Z; nibbleZ++) {
@@ -90,12 +89,15 @@ public final class ChunkUtil {
                                     continue;
                                 }
                                 BlockState block = buffer.getConnection().getMapping().getBlockState(fullBlockId);
-                                blockMap.put(new InChunkSectionPosition(nibbleX, nibbleY, nibbleZ), new BlockInfo(block));
+                                if (block == null) {
+                                    continue;
+                                }
+                                blocks[ChunkSection.Companion.getIndex(nibbleX, nibbleY, nibbleZ)] = new BlockInfo(block);
                                 arrayPos++;
                             }
                         }
                     }
-                    sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blockMap)); // ToDo
+                    sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blocks)); // ToDo
                 }
             }
             return new ChunkData(sectionMap, new DummyBiomeAccessor(buffer.getConnection().getMapping().getBiomeRegistry().get(0)), DummyLightAccessor.INSTANCE);
@@ -126,7 +128,7 @@ public final class ChunkUtil {
                 if (!BitByte.isBitSet(sectionBitMasks[0], sectionHeight)) {
                     continue;
                 }
-                HashMap<InChunkSectionPosition, BlockInfo> blockMap = new HashMap<>();
+                BlockInfo[] blocks = new BlockInfo[ProtocolDefinition.BLOCKS_PER_SECTION];
 
                 for (int nibbleY = 0; nibbleY < ProtocolDefinition.SECTION_HEIGHT_Y; nibbleY++) {
                     for (int nibbleZ = 0; nibbleZ < ProtocolDefinition.SECTION_WIDTH_Z; nibbleZ++) {
@@ -137,12 +139,12 @@ public final class ChunkUtil {
                                 arrayPos++;
                                 continue;
                             }
-                            blockMap.put(new InChunkSectionPosition(nibbleX, nibbleY, nibbleZ), new BlockInfo(block));
+                            blocks[ChunkSection.Companion.getIndex(nibbleX, nibbleY, nibbleZ)] = new BlockInfo(block);
                             arrayPos++;
                         }
                     }
                 }
-                sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blockMap));
+                sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blocks));
             }
             return new ChunkData(sectionMap, new DummyBiomeAccessor(buffer.getConnection().getMapping().getBiomeRegistry().get(0)), DummyLightAccessor.INSTANCE); // ToDo
         }
@@ -162,7 +164,7 @@ public final class ChunkUtil {
 
             long[] data = buffer.readLongArray();
 
-            HashMap<InChunkSectionPosition, BlockInfo> blockMap = new HashMap<>();
+            BlockInfo[] blocks = new BlockInfo[ProtocolDefinition.BLOCKS_PER_SECTION];
             for (int nibbleY = 0; nibbleY < ProtocolDefinition.SECTION_HEIGHT_Y; nibbleY++) {
                 for (int nibbleZ = 0; nibbleZ < ProtocolDefinition.SECTION_WIDTH_Z; nibbleZ++) {
                     for (int nibbleX = 0; nibbleX < ProtocolDefinition.SECTION_WIDTH_X; nibbleX++) {
@@ -193,7 +195,7 @@ public final class ChunkUtil {
                         if (block == null) {
                             continue;
                         }
-                        blockMap.put(new InChunkSectionPosition(nibbleX, nibbleY, nibbleZ), new BlockInfo(block));
+                        blocks[ChunkSection.Companion.getIndex(nibbleX, nibbleY, nibbleZ)] = new BlockInfo(block);
                     }
                 }
             }
@@ -206,7 +208,7 @@ public final class ChunkUtil {
                 // ToDo
             }
 
-            sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blockMap));
+            sectionMap.put(dimension.getLowestSection() + sectionHeight, new ChunkSection(blocks));
         }
         ChunkData chunkData = new ChunkData();
         chunkData.setBlocks(sectionMap);