diff --git a/hbmqtt/broker.py b/hbmqtt/broker.py
index 000e59f..6d5dcaf 100644
--- a/hbmqtt/broker.py
+++ b/hbmqtt/broker.py
@@ -8,10 +8,6 @@ import asyncio
 import sys
 import re
 from asyncio import Queue, CancelledError
-if sys.version_info < (3, 5):
-    from asyncio import async as ensure_future
-else:
-    from asyncio import ensure_future
 from collections import deque
 
 from functools import partial
@@ -29,6 +25,11 @@ from hbmqtt.adapters import (
     WebSocketsWriter)
 from .plugins.manager import PluginManager, BaseContext
 
+if sys.version_info < (3, 5):
+    from asyncio import async as ensure_future
+else:
+    from asyncio import ensure_future
+
 _defaults = {
     'timeout-disconnect-delay': 2,
     'auth': {
diff --git a/hbmqtt/mqtt/protocol/client_handler.py b/hbmqtt/mqtt/protocol/client_handler.py
index 68f97b9..d29767f 100644
--- a/hbmqtt/mqtt/protocol/client_handler.py
+++ b/hbmqtt/mqtt/protocol/client_handler.py
@@ -4,10 +4,6 @@
 import asyncio
 from asyncio import futures
 import sys
-if sys.version_info < (3, 5):
-    from asyncio import async as ensure_future
-else:
-    from asyncio import ensure_future
 from hbmqtt.mqtt.protocol.handler import ProtocolHandler, EVENT_MQTT_PACKET_RECEIVED
 from hbmqtt.mqtt.packet import *
 from hbmqtt.mqtt.disconnect import DisconnectPacket
@@ -22,6 +18,11 @@ from hbmqtt.mqtt.connack import ConnackPacket
 from hbmqtt.session import Session
 from hbmqtt.plugins.manager import PluginManager
 
+if sys.version_info < (3, 5):
+    from asyncio import async as ensure_future
+else:
+    from asyncio import ensure_future
+
 
 class ClientProtocolHandler(ProtocolHandler):
     def __init__(self, plugins_manager: PluginManager, session: Session=None, loop=None):
diff --git a/hbmqtt/plugins/manager.py b/hbmqtt/plugins/manager.py
index 3210853..2283075 100644
--- a/hbmqtt/plugins/manager.py
+++ b/hbmqtt/plugins/manager.py
@@ -9,13 +9,14 @@ import logging
 import asyncio
 import copy
 import sys
+
+from collections import namedtuple
+
 if sys.version_info < (3, 5):
     from asyncio import async as ensure_future
 else:
     from asyncio import ensure_future
 
-from collections import namedtuple
-
 Plugin = namedtuple('Plugin', ['name', 'ep', 'object'])
 
 plugins_manager = dict()
diff --git a/hbmqtt/plugins/sys/broker.py b/hbmqtt/plugins/sys/broker.py
index 04e4688..722a9ef 100644
--- a/hbmqtt/plugins/sys/broker.py
+++ b/hbmqtt/plugins/sys/broker.py
@@ -6,11 +6,12 @@ from hbmqtt.mqtt.packet import PUBLISH
 from hbmqtt.codecs import int_to_bytes_str
 import asyncio
 import sys
+from collections import deque
+
 if sys.version_info < (3, 5):
     from asyncio import async as ensure_future
 else:
     from asyncio import ensure_future
-from collections import deque
 
 DOLLAR_SYS_ROOT = '$SYS/broker/'
 STAT_BYTES_SENT = 'bytes_sent'
diff --git a/tox.ini b/tox.ini
index 16a4e4c..a549f08 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,5 @@
 [flake8]
 ignore =
-    E402,  # module level import not at top of file (~24 warnings)
     F401,  # 'x' imported but unused (~12 warnings)
     F403,  # 'from x import *' used; unable to detect undefined names (~29 warnings)
     F821,  # undefined name 'x' (~1 warnings)