diff --git a/src/pocketmine/level/format/io/ChunkUtils.php b/src/pocketmine/level/format/io/ChunkUtils.php
index 616432289..c44130f29 100644
--- a/src/pocketmine/level/format/io/ChunkUtils.php
+++ b/src/pocketmine/level/format/io/ChunkUtils.php
@@ -35,11 +35,14 @@ class ChunkUtils{
 	public static final function reorderByteArray(string $array) : string{
 		$result = str_repeat("\x00", 4096);
 		$i = 0;
+		$zM = 0;
+		$yM = 0;
 		for($x = 0; $x < 16; ++$x){
-			for($z = 0; $z < 256; $z += 16){
-				$zx = ($z + $x);
-				for($y = 0; $y < 4096; $y += 256){
-					$result{$i} = $array{$y + $zx};
+			$zM = $x + 256;
+			for($z = $x; $z < $zM; $z += 16){
+				$yM = $z + 4096;
+				for($y = $z; $y < $yM; $y += 256){
+					$result{$i} = $array{$y};
 					++$i;
 				}
 			}
@@ -51,21 +54,27 @@ class ChunkUtils{
 	 * Re-orders a nibble array (YZX -> XZY and vice versa)
 	 *
 	 * @param string $array length 2048
+	 * @param string $commonValue length 1 common value to fill the default array with and to expect, may improve sort time
 	 *
 	 * @return string length 2048
 	 */
-	public static final function reorderNibbleArray(string $array) : string{
-		$result = str_repeat("\x00", 2048);
+	public static final function reorderNibbleArray(string $array, string $commonValue = "\x00") : string{
+		$result = str_repeat($commonValue, 2048);
 		$i = 0;
 		for($x = 0; $x < 8; ++$x){
 			for($z = 0; $z < 16; ++$z){
 				$zx = (($z << 3) | $x);
 				for($y = 0; $y < 8; ++$y){
 					$j = (($y << 8) | $zx);
-					$i1 = ord($array{$j});
-					$i2 = ord($array{$j | 0x80});
-					$result{$i}        = chr(($i2 << 4) | ($i1 & 0x0f));
-					$result{$i | 0x80} = chr(($i1 >> 4) | ($i2 & 0xf0));
+					$j80 = ($j | 0x80);
+					if($array{$j} === $commonValue and $array{$j80} === $commonValue){
+						//values are already filled
+					}else{
+						$i1 = ord($array{$j});
+						$i2 = ord($array{$j80});
+						$result{$i}        = chr(($i2 << 4) | ($i1 & 0x0f));
+						$result{$i | 0x80} = chr(($i1 >> 4) | ($i2 & 0xf0));
+					}
 					$i++;
 				}
 			}
diff --git a/src/pocketmine/level/format/io/region/Anvil.php b/src/pocketmine/level/format/io/region/Anvil.php
index bf4a309a5..111c7f6a0 100644
--- a/src/pocketmine/level/format/io/region/Anvil.php
+++ b/src/pocketmine/level/format/io/region/Anvil.php
@@ -60,7 +60,7 @@ class Anvil extends McRegion{
 				"Y"          => new ByteTag("Y", $y),
 				"Blocks"     => new ByteArrayTag("Blocks", ChunkUtils::reorderByteArray($subChunk->getBlockIdArray())), //Generic in-memory chunks are currently always XZY
 				"Data"       => new ByteArrayTag("Data", ChunkUtils::reorderNibbleArray($subChunk->getBlockDataArray())),
-				"SkyLight"   => new ByteArrayTag("SkyLight", ChunkUtils::reorderNibbleArray($subChunk->getSkyLightArray())),
+				"SkyLight"   => new ByteArrayTag("SkyLight", ChunkUtils::reorderNibbleArray($subChunk->getSkyLightArray(), "\xff")),
 				"BlockLight" => new ByteArrayTag("BlockLight", ChunkUtils::reorderNibbleArray($subChunk->getBlockLightArray()))
 			]);
 		}
@@ -118,7 +118,7 @@ class Anvil extends McRegion{
 						$subChunks[$subChunk->Y->getValue()] = new SubChunk(
 							ChunkUtils::reorderByteArray($subChunk->Blocks->getValue()),
 							ChunkUtils::reorderNibbleArray($subChunk->Data->getValue()),
-							ChunkUtils::reorderNibbleArray($subChunk->SkyLight->getValue()),
+							ChunkUtils::reorderNibbleArray($subChunk->SkyLight->getValue(), "\xff"),
 							ChunkUtils::reorderNibbleArray($subChunk->BlockLight->getValue())
 						);
 					}