--- a/net/minecraft/core/Holder.java
+++ b/net/minecraft/core/Holder.java
@@ -221,7 +221,7 @@
         }
 
         void bindTags(Collection<TagKey<T>> tags) {
-            this.tags = Set.copyOf(tags);
+            this.tags = java.util.Collections.unmodifiableSet(new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>(tags)); // Paper
         }
 
         @Override
