diff --git a/src/world/format/io/region/LegacyAnvilChunkTrait.php b/src/world/format/io/region/LegacyAnvilChunkTrait.php
index 8970a2fb3..7debb29ba 100644
--- a/src/world/format/io/region/LegacyAnvilChunkTrait.php
+++ b/src/world/format/io/region/LegacyAnvilChunkTrait.php
@@ -51,7 +51,7 @@ trait LegacyAnvilChunkTrait{
 	/**
 	 * @throws CorruptedChunkException
 	 */
-	protected function deserializeChunk(string $data) : ChunkData{
+	protected function deserializeChunk(string $data) : ?ChunkData{
 		$decompressed = @zlib_decode($data);
 		if($decompressed === false){
 			throw new CorruptedChunkException("Failed to decompress chunk NBT");
diff --git a/src/world/format/io/region/McRegion.php b/src/world/format/io/region/McRegion.php
index 3367a2f81..bf1597364 100644
--- a/src/world/format/io/region/McRegion.php
+++ b/src/world/format/io/region/McRegion.php
@@ -29,6 +29,7 @@ use pocketmine\data\bedrock\BiomeIds;
 use pocketmine\nbt\BigEndianNbtSerializer;
 use pocketmine\nbt\NbtDataException;
 use pocketmine\nbt\tag\ByteArrayTag;
+use pocketmine\nbt\tag\ByteTag;
 use pocketmine\nbt\tag\CompoundTag;
 use pocketmine\nbt\tag\IntArrayTag;
 use pocketmine\nbt\tag\ListTag;
@@ -45,7 +46,7 @@ class McRegion extends RegionWorldProvider{
 	/**
 	 * @throws CorruptedChunkException
 	 */
-	protected function deserializeChunk(string $data) : ChunkData{
+	protected function deserializeChunk(string $data) : ?ChunkData{
 		$decompressed = @zlib_decode($data);
 		if($decompressed === false){
 			throw new CorruptedChunkException("Failed to decompress chunk NBT");
@@ -61,6 +62,14 @@ class McRegion extends RegionWorldProvider{
 			throw new CorruptedChunkException("'Level' key is missing from chunk NBT");
 		}
 
+		$legacyGeneratedTag = $chunk->getTag("TerrainGenerated");
+		if($legacyGeneratedTag instanceof ByteTag && $legacyGeneratedTag->getValue() === 0){
+			//In legacy PM before 3.0, PM used to save MCRegion chunks even when they weren't generated. In these cases
+			//(we'll see them in old worlds), some of the tags which we expect to always be present, will be missing.
+			//If TerrainGenerated (PM-specific tag from the olden days) is false, toss the chunk data and don't bother
+			//trying to read it.
+			return null;
+		}
 		$subChunks = [];
 		$fullIds = self::readFixedSizeByteArray($chunk, "Blocks", 32768);
 		$fullData = self::readFixedSizeByteArray($chunk, "Data", 16384);
diff --git a/src/world/format/io/region/RegionWorldProvider.php b/src/world/format/io/region/RegionWorldProvider.php
index df28c3ffe..1fe62912c 100644
--- a/src/world/format/io/region/RegionWorldProvider.php
+++ b/src/world/format/io/region/RegionWorldProvider.php
@@ -146,7 +146,7 @@ abstract class RegionWorldProvider extends BaseWorldProvider{
 	/**
 	 * @throws CorruptedChunkException
 	 */
-	abstract protected function deserializeChunk(string $data) : ChunkData;
+	abstract protected function deserializeChunk(string $data) : ?ChunkData;
 
 	/**
 	 * @return CompoundTag[]