diff --git a/src/pocketmine/nbt/tag/CompoundTag.php b/src/pocketmine/nbt/tag/CompoundTag.php
index e05e1d3d4..844213e35 100644
--- a/src/pocketmine/nbt/tag/CompoundTag.php
+++ b/src/pocketmine/nbt/tag/CompoundTag.php
@@ -82,7 +82,7 @@ class CompoundTag extends NamedTag implements \ArrayAccess{
 	 * @return NamedTag|null
 	 * @throws \RuntimeException if the tag exists and is not of the expected type (if specified)
 	 */
-	public function getTag(string $name, string $expectedType = null) : ?NamedTag{
+	public function getTag(string $name, ?string $expectedType = null) : ?NamedTag{
 		assert($expectedType === null or is_a($expectedType, NamedTag::class, true));
 		$tag = $this->{$name} ?? null;
 		if($tag !== null and $expectedType !== null and !($tag instanceof $expectedType)){