diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index 603cffb58..fb785553d 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -363,7 +363,7 @@ class Level implements ChunkManager, Metadatable{
 		$this->worldHeight = $this->provider->getWorldHeight();
 
 		$this->server->getLogger()->info($this->server->getLanguage()->translateString("pocketmine.level.preparing", [$this->displayName]));
-		$this->generator = GeneratorManager::getGenerator($this->provider->getLevelData()->getGenerator());
+		$this->generator = GeneratorManager::getGenerator($this->provider->getLevelData()->getGenerator(), true);
 		//TODO: validate generator options
 
 		$this->folderName = $name;
diff --git a/src/pocketmine/level/LevelManager.php b/src/pocketmine/level/LevelManager.php
index bae08a0e1..2ec9322c2 100644
--- a/src/pocketmine/level/LevelManager.php
+++ b/src/pocketmine/level/LevelManager.php
@@ -33,6 +33,7 @@ use pocketmine\level\format\io\LevelProvider;
 use pocketmine\level\format\io\LevelProviderManager;
 use pocketmine\level\format\io\WritableLevelProvider;
 use pocketmine\level\generator\Generator;
+use pocketmine\level\generator\GeneratorManager;
 use pocketmine\level\generator\normal\Normal;
 use pocketmine\Server;
 use pocketmine\timings\Timings;
@@ -217,10 +218,16 @@ class LevelManager{
 		$providerClass = array_shift($providers);
 
 		/**
-		 * @var LevelProvider
+		 * @var LevelProvider $provider
 		 * @see LevelProvider::__construct()
 		 */
 		$provider = new $providerClass($path);
+		try{
+			GeneratorManager::getGenerator($provider->getLevelData()->getGenerator(), true);
+		}catch(\InvalidArgumentException $e){
+			$this->server->getLogger()->error($this->server->getLanguage()->translateString("pocketmine.level.loadError", [$name, "Unknown generator \"" . $provider->getLevelData()->getGenerator() . "\""]));
+			return false;
+		}
 		if(!($provider instanceof WritableLevelProvider)){
 			if(!$autoUpgrade){
 				throw new LevelException("World \"$name\" is in an unsupported format and needs to be upgraded");
diff --git a/src/pocketmine/level/generator/GeneratorManager.php b/src/pocketmine/level/generator/GeneratorManager.php
index ee61cecd0..765499ab3 100644
--- a/src/pocketmine/level/generator/GeneratorManager.php
+++ b/src/pocketmine/level/generator/GeneratorManager.php
@@ -74,14 +74,19 @@ final class GeneratorManager{
 	 * Returns a class name of a registered Generator matching the given name.
 	 *
 	 * @param string $name
+	 * @param bool   $throwOnMissing @deprecated this is for backwards compatibility only
 	 *
 	 * @return string|Generator Name of class that extends Generator (not an actual Generator object)
+	 * @throws \InvalidArgumentException if the generator type isn't registered
 	 */
-	public static function getGenerator(string $name){
+	public static function getGenerator(string $name, bool $throwOnMissing = false){
 		if(isset(self::$list[$name = strtolower($name)])){
 			return self::$list[$name];
 		}
 
+		if($throwOnMissing){
+			throw new \InvalidArgumentException("Alias \"$name\" does not map to any known generator");
+		}
 		return Normal::class;
 	}