diff --git a/requirements-dev.txt b/requirements-dev.txt
index f89b93afaf..811e308111 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -3,6 +3,6 @@
 pytest>=3.6
 flake8
 protobuf
-isort
+isort==4.3.10
 black; python_version >= "3.6"
 autoflake>=1.2
diff --git a/trezorlib/transport/bridge.py b/trezorlib/transport/bridge.py
index b44949b7ce..207f2854a2 100644
--- a/trezorlib/transport/bridge.py
+++ b/trezorlib/transport/bridge.py
@@ -21,8 +21,8 @@ from typing import Any, Dict, Iterable, Optional
 
 import requests
 
-from . import Transport, TransportException
 from .. import mapping, protobuf
+from . import Transport, TransportException
 
 LOG = logging.getLogger(__name__)
 
diff --git a/trezorlib/transport/protocol.py b/trezorlib/transport/protocol.py
index 05bff36ff2..9fe658f627 100644
--- a/trezorlib/transport/protocol.py
+++ b/trezorlib/transport/protocol.py
@@ -22,8 +22,8 @@ from typing import Tuple
 
 from typing_extensions import Protocol as StructuralType
 
-from . import Transport
 from .. import mapping, protobuf
+from . import Transport
 
 REPLEN = 64