diff --git a/common/src/main/java/net/irisshaders/iris/shaderpack/materialmap/BlockMaterialMapping.java b/common/src/main/java/net/irisshaders/iris/shaderpack/materialmap/BlockMaterialMapping.java
index 8f5f2c4e7b..88f78d9074 100644
--- a/common/src/main/java/net/irisshaders/iris/shaderpack/materialmap/BlockMaterialMapping.java
+++ b/common/src/main/java/net/irisshaders/iris/shaderpack/materialmap/BlockMaterialMapping.java
@@ -23,7 +23,7 @@
 public class BlockMaterialMapping {
 	public static Object2IntMap<BlockState> createBlockStateIdMap(Int2ObjectLinkedOpenHashMap<List<BlockEntry>> blockPropertiesMap, Int2ObjectLinkedOpenHashMap<List<TagEntry>> tagPropertiesMap) {
 		Object2IntMap<BlockState> blockStateIds = new Object2IntLinkedOpenHashMap<>();
-
+		blockStateIds.defaultReturnValue(-1);
 		blockPropertiesMap.forEach((intId, entries) -> {
 			for (BlockEntry entry : entries) {
 				addBlockStates(entry, blockStateIds, intId);