diff --git a/pycardano/txbuilder.py b/pycardano/txbuilder.py
index d99fb20d..dd83fbb4 100644
--- a/pycardano/txbuilder.py
+++ b/pycardano/txbuilder.py
@@ -1204,7 +1204,7 @@ def build_witness_set(
                         f"Unsupported script type: {type(script)}"
                     )
 
-        return TransactionWitnessSet(
+        witness_set = TransactionWitnessSet(
             native_scripts=native_scripts if native_scripts else None,
             plutus_v1_script=plutus_v1_scripts if plutus_v1_scripts else None,
             plutus_v2_script=plutus_v2_scripts if plutus_v2_scripts else None,
@@ -1212,6 +1212,8 @@ def build_witness_set(
             redeemer=self.redeemers() if self._redeemer_list else None,
             plutus_data=plutus_data if plutus_data else None,
         )
+        witness_set.convert_to_latest_spec()
+        return witness_set
 
     def _ensure_no_input_exclusion_conflict(self):
         intersection = set(self.inputs).intersection(set(self.excluded_inputs))
diff --git a/pycardano/witness.py b/pycardano/witness.py
index 54a94ce7..52690a3f 100644
--- a/pycardano/witness.py
+++ b/pycardano/witness.py
@@ -108,7 +108,7 @@ class TransactionWitnessSet(MapCBORSerializable):
         },
     )
 
-    plutus_data: Optional[Union[IndefiniteList, List[Any], NonEmptyOrderedSet[Any]]] = (
+    plutus_data: Optional[Union[List[Any], IndefiniteList, NonEmptyOrderedSet[Any]]] = (
         field(
             default=None,
             metadata={"optional": True, "key": 4},
@@ -140,7 +140,7 @@ class TransactionWitnessSet(MapCBORSerializable):
         },
     )
 
-    def __post_init__(self):
+    def convert_to_latest_spec(self):
         # Convert lists to NonEmptyOrderedSet for fields that should use NonEmptyOrderedSet
         if isinstance(self.vkey_witnesses, list):
             self.vkey_witnesses = NonEmptyOrderedSet(self.vkey_witnesses)
diff --git a/test/pycardano/test_serialization.py b/test/pycardano/test_serialization.py
index f4edfe65..65b9d1ef 100644
--- a/test/pycardano/test_serialization.py
+++ b/test/pycardano/test_serialization.py
@@ -761,6 +761,7 @@ def test_transaction_witness_set_with_ordered_sets():
 
     # Test conversion from list to NonEmptyOrderedSet
     witness_set = TransactionWitnessSet(vkey_witnesses=[witness])
+    witness_set.convert_to_latest_spec()
     assert isinstance(witness_set.vkey_witnesses, NonEmptyOrderedSet)
     assert witness in witness_set.vkey_witnesses
 
@@ -772,11 +773,13 @@ def test_transaction_witness_set_with_ordered_sets():
 
     # Test empty list conversion
     witness_set = TransactionWitnessSet(vkey_witnesses=[])
+    witness_set.convert_to_latest_spec()
     with pytest.raises(ValueError, match="NonEmptyOrderedSet cannot be empty"):
         witness_set.to_validated_primitive()
 
     # Test None value
     witness_set = TransactionWitnessSet(vkey_witnesses=None)
+    witness_set.convert_to_latest_spec()
     primitive = witness_set.to_primitive()
     restored = TransactionWitnessSet.from_primitive(primitive)
     assert restored.vkey_witnesses is None
diff --git a/test/pycardano/test_witness.py b/test/pycardano/test_witness.py
index 65752c72..b4291034 100644
--- a/test/pycardano/test_witness.py
+++ b/test/pycardano/test_witness.py
@@ -1,6 +1,14 @@
+import json
 import tempfile
 
-from pycardano import PaymentSigningKey, PaymentVerificationKey, VerificationKeyWitness
+from pycardano import (
+    PaymentSigningKey,
+    PaymentVerificationKey,
+    Transaction,
+    TransactionWitnessSet,
+    Unit,
+    VerificationKeyWitness,
+)
 
 
 def test_witness_save_load():
@@ -17,3 +25,10 @@ def test_witness_save_load():
         assert witness == loaded_witness
 
         assert witness != vk
+
+
+def test_redeemer_decode():
+    witness = TransactionWitnessSet(plutus_data=[Unit()])
+    encoded = witness.to_cbor()
+    decoded = TransactionWitnessSet.from_cbor(encoded)
+    assert isinstance(decoded.plutus_data, list)