diff --git a/python/src/trezorlib/btc.py b/python/src/trezorlib/btc.py
index 1afd95a0e17..9982513ee20 100644
--- a/python/src/trezorlib/btc.py
+++ b/python/src/trezorlib/btc.py
@@ -20,6 +20,7 @@
 from typing import TYPE_CHECKING, Any, Dict, Sequence, Tuple
 
 from . import exceptions, messages
+from .messages.SignTx import EnumTypeAmountUnit
 from .tools import expect, normalize_nfc, session
 
 if TYPE_CHECKING:
@@ -186,9 +187,10 @@ def sign_tx(
     coin_name: str,
     inputs: Sequence[messages.TxInputType],
     outputs: Sequence[messages.TxOutputType],
-    details: messages.SignTx = None,
+    details: messages.ButtonRequestType = None,
     prev_txes: Dict[bytes, messages.TransactionType] = None,
     preauthorized: bool = False,
+    amount_unit: EnumTypeAmountUnit = None,
     **kwargs: Any,
 ) -> Tuple[Sequence[bytes], bytes]:
     """Sign a Bitcoin-like transaction.
diff --git a/tests/device_tests/test_msg_signtx_amount_unit.py b/tests/device_tests/test_msg_signtx_amount_unit.py
new file mode 100644
index 00000000000..70ca8ac60da
--- /dev/null
+++ b/tests/device_tests/test_msg_signtx_amount_unit.py
@@ -0,0 +1,71 @@
+# This file is part of the Trezor project.
+#
+# Copyright (C) 2012-2020 SatoshiLabs and contributors
+#
+# This library is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License version 3
+# as published by the Free Software Foundation.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the License along with this library.
+# If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
+
+import pytest
+
+from trezorlib import btc, messages as proto
+from trezorlib.tools import parse_path
+
+from ..tx_cache import TxCache
+
+TX_API = TxCache("Testnet")
+
+TXHASH_091446 = bytes.fromhex(
+    "09144602765ce3dd8f4329445b20e3684e948709c5cdcaf12da3bb079c99448a"
+)
+
+VECTORS = (  # amount_unit
+    None,
+    proto.AmountUnit.BITCOIN,
+    proto.AmountUnit.MILLIBITCOIN,
+    proto.AmountUnit.MICROBITCOIN,
+    proto.AmountUnit.SATOSHI,
+)
+
+
+@pytest.mark.parametrize("amount_unit", VECTORS)
+def test_signtx(client, amount_unit):
+    inp1 = proto.TxInputType(
+        address_n=parse_path("84'/1'/0'/0/0"),
+        amount=12300000,
+        prev_hash=TXHASH_091446,
+        prev_index=0,
+        script_type=proto.InputScriptType.SPENDWITNESS,
+    )
+    out1 = proto.TxOutputType(
+        address="2N4Q5FhU2497BryFfUgbqkAJE87aKHUhXMp",
+        amount=5000000,
+        script_type=proto.OutputScriptType.PAYTOADDRESS,
+    )
+    out2 = proto.TxOutputType(
+        address="tb1q694ccp5qcc0udmfwgp692u2s2hjpq5h407urtu",
+        script_type=proto.OutputScriptType.PAYTOADDRESS,
+        amount=12300000 - 11000 - 5000000,
+    )
+    with client:
+        _, serialized_tx = btc.sign_tx(
+            client,
+            "Testnet",
+            [inp1],
+            [out1, out2],
+            prev_txes=TX_API,
+            amount_unit=amount_unit,
+        )
+
+    assert (
+        serialized_tx.hex()
+        == "010000000001018a44999c07bba32df1cacdc50987944e68e3205b4429438fdde35c76024614090000000000ffffffff02404b4c000000000017a9147a55d61848e77ca266e79a39bfc85c580a6426c987a8386f0000000000160014d16b8c0680c61fc6ed2e407455715055e41052f502473044022073ce72dcf2f6e42eeb44adbe7d5038cf3763f168d1c04bd8b873a19b53331f51022016b051725731e7f53a567021bcd9c370727f551c81e857ebae7c128472119652012103adc58245cf28406af0ef5cc24b8afba7f1be6c72f279b642d85c48798685f86200000000"
+    )