diff --git a/pycardano/backend/ogmios.py b/pycardano/backend/ogmios.py
index ddffb9a4..63ffaf14 100644
--- a/pycardano/backend/ogmios.py
+++ b/pycardano/backend/ogmios.py
@@ -359,8 +359,6 @@ def _utxos_kupo(self, address: str) -> List[UTxO]:
                 )
                 if datum_hash and result.get("datum_type", "inline"):
                     datum = self._get_datum_from_kupo(result["datum_hash"])
-                    if datum is not None:
-                        datum_hash = None
 
                 if not result["value"]["assets"]:
                     tx_out = TransactionOutput(
diff --git a/pycardano/txbuilder.py b/pycardano/txbuilder.py
index 52a0f989..154ae651 100644
--- a/pycardano/txbuilder.py
+++ b/pycardano/txbuilder.py
@@ -236,6 +236,15 @@ def add_script_input(
                 f"Datum hash in transaction output is {utxo.output.datum_hash}, "
                 f"but actual datum hash from input datum is {datum_hash(datum)}."
             )
+        if (
+            datum is not None
+            and utxo.output.datum_hash is None
+            and utxo.output.datum is not None
+        ):
+            raise InvalidArgumentException(
+                f"Inline Datum found in transaction output {utxo.input}, "
+                "so attaching a Datum to the transaction input manually is not allowed."
+            )
 
         if datum is not None:
             self.datums[datum_hash(datum)] = datum
diff --git a/test/pycardano/test_txbuilder.py b/test/pycardano/test_txbuilder.py
index 7ba70819..a362da6d 100644
--- a/test/pycardano/test_txbuilder.py
+++ b/test/pycardano/test_txbuilder.py
@@ -1032,6 +1032,30 @@ def test_estimate_execution_unit(chain_context):
     assert [plutus_script] == witness.plutus_v1_script
 
 
+def test_add_script_input_inline_datum_extra(chain_context):
+    tx_builder = TransactionBuilder(chain_context)
+    tx_in1 = TransactionInput.from_primitive(
+        ["18cbe6cadecd3f89b60e08e68e5e6c7d72d730aaa1ad21431590f7e6643438ef", 0]
+    )
+    tx_in2 = TransactionInput.from_primitive(
+        ["18cbe6cadecd3f89b60e08e68e5e6c7d72d730aaa1ad21431590f7e6643438ef", 1]
+    )
+    plutus_script = PlutusV1Script(b"dummy test script")
+    script_hash = plutus_script_hash(plutus_script)
+    script_address = Address(script_hash)
+    datum = PlutusData()
+    utxo1 = UTxO(tx_in1, TransactionOutput(script_address, 10000000, datum=datum))
+    redeemer1 = Redeemer(PlutusData(), ExecutionUnits(1000000, 1000000))
+    pytest.raises(
+        InvalidArgumentException,
+        tx_builder.add_script_input,
+        utxo1,
+        plutus_script,
+        datum,
+        redeemer1,
+    )
+
+
 def test_tx_builder_exact_fee_no_change(chain_context):
     tx_builder = TransactionBuilder(chain_context)
     sender = "addr_test1vrm9x2zsux7va6w892g38tvchnzahvcd9tykqf3ygnmwtaqyfg52x"