diff --git a/src/block/UnknownBlock.php b/src/block/UnknownBlock.php
index 02b125e98..75afd32b2 100644
--- a/src/block/UnknownBlock.php
+++ b/src/block/UnknownBlock.php
@@ -36,6 +36,8 @@ class UnknownBlock extends Transparent{
 		$this->stateData = $stateData;
 	}
 
+	public function getRequiredTypeDataBits() : int{ return Block::INTERNAL_STATE_DATA_BITS; }
+
 	protected function describeType(RuntimeDataReader|RuntimeDataWriter $w) : void{
 		//use type instead of state, so we don't lose any information like colour
 		//this might be an improperly registered plugin block