diff --git a/core/src/trezor/wire/thp/channel.py b/core/src/trezor/wire/thp/channel.py
index a01e4295dd..0f60dfa774 100644
--- a/core/src/trezor/wire/thp/channel.py
+++ b/core/src/trezor/wire/thp/channel.py
@@ -132,7 +132,7 @@ class Channel:
                 # TODO Check CRC and if valid, check tag, if valid update nonces
                 self._finish_fallback()
                 # TODO self.write() failure device is busy - use channel buffer to send this failure message!!
-                return
+                return None
             return received_message_handler.handle_received_message(self, buffer)
         elif self.expected_payload_length + INIT_HEADER_LENGTH > self.bytes_read:
             self.is_cont_packet_expected = True
diff --git a/core/tests/test_apps.bitcoin.approver.py b/core/tests/test_apps.bitcoin.approver.py
index d691648b64..408f96d7ee 100644
--- a/core/tests/test_apps.bitcoin.approver.py
+++ b/core/tests/test_apps.bitcoin.approver.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 
 import storage.cache_codec
diff --git a/core/tests/test_apps.bitcoin.authorization.py b/core/tests/test_apps.bitcoin.authorization.py
index 4faf202989..aedcadba92 100644
--- a/core/tests/test_apps.bitcoin.authorization.py
+++ b/core/tests/test_apps.bitcoin.authorization.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 
 import storage.cache_codec
diff --git a/core/tests/test_storage.cache.py b/core/tests/test_storage.cache.py
index 0837d76b92..1e43e09d98 100644
--- a/core/tests/test_storage.cache.py
+++ b/core/tests/test_storage.cache.py
@@ -378,7 +378,7 @@ class TestStorageCache(unittest.TestCase):
             session_id = cache_codec.start_session()
             self.assertEqual(cache_codec.start_session(session_id), session_id)
             get_active_session().set(KEY, b"A")
-            for i in range(_PROTOCOL_CACHE._MAX_SESSIONS_COUNT):
+            for _ in range(_PROTOCOL_CACHE._MAX_SESSIONS_COUNT):
                 cache_codec.start_session()
             self.assertNotEqual(cache_codec.start_session(session_id), session_id)
             self.assertIsNone(get_active_session().get(KEY))
diff --git a/core/tests/test_trezor.wire.thp.checksum.py b/core/tests/test_trezor.wire.thp.checksum.py
index 41c9325001..f5d59d6805 100644
--- a/core/tests/test_trezor.wire.thp.checksum.py
+++ b/core/tests/test_trezor.wire.thp.checksum.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 
 if utils.USE_THP:
diff --git a/core/tests/test_trezor.wire.thp.crypto.py b/core/tests/test_trezor.wire.thp.crypto.py
index d26785ce65..1eee57f8cb 100644
--- a/core/tests/test_trezor.wire.thp.crypto.py
+++ b/core/tests/test_trezor.wire.thp.crypto.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 from trezorcrypto import aesgcm, curve25519
 
@@ -101,8 +102,8 @@ class TestTrezorHostProtocolCrypto(unittest.TestCase):
 
     def test_iv_from_nonce(self):
         for v in self.vectors_iv:
-            x = v[0]
-            y = x.to_bytes(8, "big")
+            # x = v[0]
+            # y = x.to_bytes(8, "big")
             iv = crypto._get_iv_from_nonce(v[0])
             self.assertEqual(iv, v[1])
         with self.assertRaises(AssertionError) as e:
diff --git a/core/tests/test_trezor.wire.thp.py b/core/tests/test_trezor.wire.thp.py
index 1599a59307..f4e0bce287 100644
--- a/core/tests/test_trezor.wire.thp.py
+++ b/core/tests/test_trezor.wire.thp.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 from mock_wire_interface import MockHID
 from trezor import config, io, protobuf
@@ -256,7 +257,7 @@ class TestTrezorHostProtocol(unittest.TestCase):
 
         # test invalid tag in handshake phase
         cid_2 = get_channel_id_from_response(expected_response_1)
-        cid_2_bytes = cid_2.to_bytes(2, "big")
+        # cid_2_bytes = cid_2.to_bytes(2, "big")
         channel = thp_main._CHANNELS[cid_2]
         channel.iface = self.interface
 
diff --git a/core/tests/test_trezor.wire.thp.writer.py b/core/tests/test_trezor.wire.thp.writer.py
index ecaec3c61a..0f6110761a 100644
--- a/core/tests/test_trezor.wire.thp.writer.py
+++ b/core/tests/test_trezor.wire.thp.writer.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 
 from typing import Any, Awaitable
diff --git a/core/tests/test_trezor.wire.thp_deprecated.py b/core/tests/test_trezor.wire.thp_deprecated.py
index 550b29e64d..49f2256e69 100644
--- a/core/tests/test_trezor.wire.thp_deprecated.py
+++ b/core/tests/test_trezor.wire.thp_deprecated.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from common import *  # isort:skip
 import ustruct
 from typing import TYPE_CHECKING
diff --git a/core/tests/thp_common.py b/core/tests/thp_common.py
index d22243d29e..86a023d3c6 100644
--- a/core/tests/thp_common.py
+++ b/core/tests/thp_common.py
@@ -1,3 +1,4 @@
+# flake8: noqa: F403,F405
 from trezor import utils
 from trezor.wire.thp import ChannelState