diff --git a/MCGalaxy/Blocks/BlockDefinitions.cs b/MCGalaxy/Blocks/BlockDefinitions.cs
index f238f2d70..f04a0a618 100644
--- a/MCGalaxy/Blocks/BlockDefinitions.cs
+++ b/MCGalaxy/Blocks/BlockDefinitions.cs
@@ -341,7 +341,7 @@ namespace MCGalaxy {
                 if (pl.hasBlockDefs) continue;
                 
                 // if custom block is replacing core block, need to always reload for fallback
-                if (block >= Block.CpeCount && !pl.level.MayHaveCustomBlocks) continue;                
+                if (block >= Block.CpeCount && !pl.level.MightHaveCustomBlocks()) continue;
                 PlayerActions.ReloadMap(pl);
             }
         }
diff --git a/MCGalaxy/Levels/Level.Blocks.cs b/MCGalaxy/Levels/Level.Blocks.cs
index 05e06ac25..eefcd93b0 100644
--- a/MCGalaxy/Levels/Level.Blocks.cs
+++ b/MCGalaxy/Levels/Level.Blocks.cs
@@ -33,16 +33,15 @@ namespace MCGalaxy {
         public byte[][] CustomBlocks;
         public int ChunksX, ChunksY, ChunksZ;
         
-        public bool MayHaveCustomBlocks {
-            get {
-                byte[][] customBlocks = CustomBlocks;
-                if (customBlocks == null) return false;
+        /// <summary> Relatively quick guess at whether this map might use custom blocks. </summary>
+        public bool MightHaveCustomBlocks() {
+            byte[][] customBlocks = CustomBlocks;
+            if (customBlocks == null) return false;
                 
-                for (int i = 0; i < customBlocks.Length; i++) {
-                    if (customBlocks[i] != null) return true;
-                }
-                return false;
+            for (int i = 0; i < customBlocks.Length; i++) {
+                if (customBlocks[i] != null) return true;
             }
+            return false;
         }
         
         
@@ -390,7 +389,7 @@ namespace MCGalaxy {
                     AddCheck(b, false, data);
                 }
                 
-                // Save bandwidth sending identical looking blocks, like air/op_air changes.
+                // Save bandwidth not sending identical looking blocks, like air/op_air changes.
                 return !Block.VisuallyEquals(old, block);
             } catch {
                 return false;
diff --git a/MCGalaxy/Network/Player.Networking.cs b/MCGalaxy/Network/Player.Networking.cs
index 70af3b9ec..a09d64b43 100644
--- a/MCGalaxy/Network/Player.Networking.cs
+++ b/MCGalaxy/Network/Player.Networking.cs
@@ -251,10 +251,10 @@ namespace MCGalaxy {
                 using (LevelChunkStream dst = new LevelChunkStream(this))
                     using (Stream stream = LevelChunkStream.CompressMapHeader(this, volume, dst))
                 {
-                    if (!level.MayHaveCustomBlocks) {
-                        LevelChunkStream.CompressMapSimple(this, stream, dst);
-                    } else {
+                	if (level.MightHaveCustomBlocks()) {
                         LevelChunkStream.CompressMap(this, stream, dst);
+                	} else {
+                        LevelChunkStream.CompressMapSimple(this, stream, dst);
                     }
                 }
                 
diff --git a/MCGalaxy/Network/Utils/LevelChunkStream.cs b/MCGalaxy/Network/Utils/LevelChunkStream.cs
index 8ac94eec5..f4198ca26 100644
--- a/MCGalaxy/Network/Utils/LevelChunkStream.cs
+++ b/MCGalaxy/Network/Utils/LevelChunkStream.cs
@@ -84,14 +84,16 @@ namespace MCGalaxy.Network {
         }
         
         
-        internal static Stream CompressMapHeader(Player player, int volume, LevelChunkStream dst) {
+        public static Stream CompressMapHeader(Player p, int volume, LevelChunkStream dst) {
             Stream stream = null;
-            if (player.Supports(CpeExt.FastMap)) {
+            if (p.Supports(CpeExt.FastMap)) {
                 stream = new DeflateStream(dst, CompressionMode.Compress, true);
             } else {
                 stream = new GZipStream(dst, CompressionMode.Compress, true);
-                byte[] buffer = new byte[4]; NetUtils.WriteI32(volume, buffer, 0);
-                stream.Write(buffer, 0, sizeof(int));
+                byte[] buffer = new byte[4];
+                
+                NetUtils.WriteI32(volume, buffer, 0);
+                stream.Write(buffer, 0, 4);
             }
             return stream;
         }
@@ -117,7 +119,7 @@ namespace MCGalaxy.Network {
                 bIndex++;
                 
                 if (bIndex == bufferSize) {
-                    // '0' to indicate classic blocks
+                    // '0' to indicate this chunk has lower 8 bits of block ids
                     dst.chunkValue = p.hasExtBlocks ? (byte)0 : (byte)(i * progScale);
                     stream.Write(buffer, 0, bufferSize); bIndex = 0;
                 }
@@ -132,7 +134,7 @@ namespace MCGalaxy.Network {
             
             // Store on stack instead of performing function call for every block in map
             byte* conv = stackalloc byte[Block.ExtendedCount];
-            byte* convExt = conv + Block.Count;
+            byte* convExt  = conv + Block.Count;
             #if TEN_BIT_BLOCKS
             byte* convExt2 = conv + Block.Count * 2;
             byte* convExt3 = conv + Block.Count * 3;