diff --git a/src/pocketmine/Server.php b/src/pocketmine/Server.php
index 736a06f84..82f7d204d 100644
--- a/src/pocketmine/Server.php
+++ b/src/pocketmine/Server.php
@@ -2186,7 +2186,7 @@ class Server{
 	private function tickProcessor(){
 		while($this->isRunning){
 			$this->tick();
-			usleep((int) max(1, ($this->nextTick - microtime(true)) * 1000000));
+			usleep((int) max(1, ($this->nextTick - microtime(true)) * 1000000 - 2000));
 		}
 	}
 
@@ -2369,7 +2369,7 @@ class Server{
 	 */
 	private function tick(){
 		$tickTime = microtime(true);
-		if($tickTime < $this->nextTick){
+		if(($tickTime - $this->nextTick) < -0.025){ //Allow half a tick of diff
 			return false;
 		}
 
diff --git a/src/pocketmine/event/HandlerList.php b/src/pocketmine/event/HandlerList.php
index cc4d680fe..3d66a3461 100644
--- a/src/pocketmine/event/HandlerList.php
+++ b/src/pocketmine/event/HandlerList.php
@@ -151,7 +151,7 @@ class HandlerList{
 	 * @return RegisteredListener[]
 	 */
 	public function getRegisteredListeners($plugin = null){
-		if($plugin instanceof Plugin){
+		if($plugin !== null){
 			$listeners = [];
 			foreach($this->getRegisteredListeners(null) as $hash => $listener){
 				if($listener->getPlugin() === $plugin){
diff --git a/src/pocketmine/level/format/FullChunk.php b/src/pocketmine/level/format/FullChunk.php
index 548d8235e..f1406bda9 100644
--- a/src/pocketmine/level/format/FullChunk.php
+++ b/src/pocketmine/level/format/FullChunk.php
@@ -176,6 +176,8 @@ interface FullChunk{
 	 */
 	public function setHeightMap($x, $z, $value);
 
+	public function recalculateHeightMap();
+
 	/**
 	 * @param int $x 0-15
 	 * @param int $z 0-15
diff --git a/src/pocketmine/level/format/generic/BaseFullChunk.php b/src/pocketmine/level/format/generic/BaseFullChunk.php
index 1dff0be2f..bcd0bdfbe 100644
--- a/src/pocketmine/level/format/generic/BaseFullChunk.php
+++ b/src/pocketmine/level/format/generic/BaseFullChunk.php
@@ -151,12 +151,6 @@ abstract class BaseFullChunk implements FullChunk{
 
 			$this->getProvider()->getLevel()->timings->syncChunkLoadTileEntitiesTimer->stopTiming();
 
-			for($z = 0; $z < 16; ++$z){
-				for($x = 0; $x < 16; ++$x){
-					$this->setHeightMap($x, $z, $this->getHighestBlockAt($x, $z));
-				}
-			}
-
 			$this->NBTentities = null;
 			$this->NBTtiles = null;
 			$this->hasChanged = false;
@@ -228,10 +222,27 @@ abstract class BaseFullChunk implements FullChunk{
 		$this->heightMap[($z << 4) + $x] = $value;
 	}
 
-	public function getHighestBlockAt($x, $z){
+	public function recalculateHeightMap(){
+		for($z = 0; $z < 16; ++$z){
+			for($x = 0; $x < 16; ++$x){
+				$this->setHeightMap($x, $z, $this->getHighestBlockAt($x, $z, false));
+			}
+		}
+	}
+
+	public function getHighestBlockAt($x, $z, $cache = true){
+		if($cache){
+			$h = $this->getHeightMap($x, $z);
+
+			if($h !== 0 and $h !== 127){
+				return $h;
+			}
+		}
+
 		$column = $this->getBlockIdColumn($x, $z);
 		for($y = 127; $y >= 0; --$y){
 			if($column{$y} !== "\x00"){
+				$this->setHeightMap($x, $z, $y);
 				return $y;
 			}
 		}
diff --git a/src/pocketmine/level/format/mcregion/RegionLoader.php b/src/pocketmine/level/format/mcregion/RegionLoader.php
index 10a6eb008..80599ccaa 100644
--- a/src/pocketmine/level/format/mcregion/RegionLoader.php
+++ b/src/pocketmine/level/format/mcregion/RegionLoader.php
@@ -169,7 +169,7 @@ class RegionLoader{
 		$full = $half . $half;
 		$nbt->Blocks = new ByteArray("Blocks", $full);
 		$nbt->Data = new ByteArray("Data", $half);
-		$nbt->SkyLight = new ByteArray("SkyLight", $half);
+		$nbt->SkyLight = new ByteArray("SkyLight", str_repeat("\xff", 16384));
 		$nbt->BlockLight = new ByteArray("BlockLight", $half);
 
 		$nbt->Entities = new Enum("Entities", []);
diff --git a/src/pocketmine/level/generator/PopulationTask.php b/src/pocketmine/level/generator/PopulationTask.php
index 825260790..a484f9862 100644
--- a/src/pocketmine/level/generator/PopulationTask.php
+++ b/src/pocketmine/level/generator/PopulationTask.php
@@ -106,6 +106,7 @@ class PopulationTask extends AsyncTask{
 		$generator->populateChunk($chunk->getX(), $chunk->getZ());
 
 		$chunk = $manager->getChunk($chunk->getX(), $chunk->getZ());
+		$chunk->recalculateHeightMap();
 		$chunk->setPopulated(true);
 		$this->chunk = $chunk->toFastBinary();
 
diff --git a/src/pocketmine/level/generator/normal/Normal.php b/src/pocketmine/level/generator/normal/Normal.php
index b61f7f6d0..804d1d95d 100644
--- a/src/pocketmine/level/generator/normal/Normal.php
+++ b/src/pocketmine/level/generator/normal/Normal.php
@@ -251,7 +251,7 @@ class Normal extends Generator{
 
 					if($noiseValue >= 0){
 						$chunk->setBlockId($x, $y, $z, Block::STONE);
-					}else{
+					}/*else{
 						if($y <= $this->waterHeight){
 							$chunk->setBlockId($x, $y, $z, Block::STILL_WATER);
 							$lightValue = 15 - ($this->waterHeight - $y) * 2;
@@ -261,7 +261,7 @@ class Normal extends Generator{
 						}else{
 							$chunk->setBlockSkyLight($x, $y, $z, 15);
 						}
-					}
+					}*/
 				}
 			}
 		}