diff --git a/src/pocketmine/level/format/generic/EmptySubChunk.php b/src/pocketmine/level/format/generic/EmptySubChunk.php
index acdbccce7..953df4771 100644
--- a/src/pocketmine/level/format/generic/EmptySubChunk.php
+++ b/src/pocketmine/level/format/generic/EmptySubChunk.php
@@ -19,6 +19,8 @@
  *
 */
 
+declare(strict_types = 1);
+
 namespace pocketmine\level\format\generic;
 
 use pocketmine\utils\ChunkException;
diff --git a/src/pocketmine/level/format/generic/SubChunk.php b/src/pocketmine/level/format/generic/SubChunk.php
index 630bfaae3..a9b52e585 100644
--- a/src/pocketmine/level/format/generic/SubChunk.php
+++ b/src/pocketmine/level/format/generic/SubChunk.php
@@ -19,6 +19,8 @@
  *
 */
 
+declare(strict_types = 1);
+
 namespace pocketmine\level\format\generic;
 
 class SubChunk{