diff --git a/ext/java/org/msgpack/jruby/Factory.java b/ext/java/org/msgpack/jruby/Factory.java
index 5973f8fb..dac2666d 100644
--- a/ext/java/org/msgpack/jruby/Factory.java
+++ b/ext/java/org/msgpack/jruby/Factory.java
@@ -59,6 +59,7 @@ public IRubyObject dup() {
     Factory clone = (Factory)super.dup();
     clone.extensionRegistry = extensionRegistry();
     clone.hasSymbolExtType = hasSymbolExtType;
+    clone.hasBigIntExtType = hasBigIntExtType;
     return clone;
   }
 
diff --git a/ext/msgpack/factory_class.c b/ext/msgpack/factory_class.c
index 1eeb0081..c4683a2a 100644
--- a/ext/msgpack/factory_class.c
+++ b/ext/msgpack/factory_class.c
@@ -121,7 +121,10 @@ static VALUE Factory_dup(VALUE self)
     msgpack_factory_t *fc = Factory_get(self);
     msgpack_factory_t *cloned_fc = Factory_get(clone);
 
+    cloned_fc->has_bigint_ext_type = fc->has_bigint_ext_type;
     cloned_fc->has_symbol_ext_type = fc->has_symbol_ext_type;
+    cloned_fc->optimized_symbol_ext_type = fc->optimized_symbol_ext_type;
+    cloned_fc->symbol_ext_type = fc->symbol_ext_type;
     cloned_fc->pkrg = fc->pkrg;
     msgpack_unpacker_ext_registry_borrow(fc->ukrg, &cloned_fc->ukrg);
     msgpack_packer_ext_registry_dup(clone, &fc->pkrg, &cloned_fc->pkrg);
@@ -230,6 +233,7 @@ static VALUE Factory_register_type_internal(VALUE self, VALUE rb_ext_type, VALUE
     }
 
     if(ext_module == rb_cSymbol) {
+        fc->symbol_ext_type = ext_type;
         if(NIL_P(options) || RTEST(rb_hash_aref(options, ID2SYM(rb_intern("packer"))))) {
             fc->has_symbol_ext_type = true;
         }
diff --git a/spec/factory_spec.rb b/spec/factory_spec.rb
index b8fefee7..d86cac4c 100644
--- a/spec/factory_spec.rb
+++ b/spec/factory_spec.rb
@@ -512,10 +512,10 @@ def roundtrip(object, options = nil)
       before do
         skip if IS_JRUBY # JRuby implementation doesn't support the optimized symbols unpacker for now
         subject.register_type(
-          0x00,
+          0x01,
           ::Symbol,
           packer: :to_msgpack_ext,
-          unpacker: :from_msgpack_ext,
+          unpacker: ->(_) { raise "symbol unpacking not optimized" },
           optimized_symbols_parsing: true,
         )
       end