diff --git a/docs/misc/changelog.rst b/docs/misc/changelog.rst
index c1d9461e2..f5cf0b6e9 100644
--- a/docs/misc/changelog.rst
+++ b/docs/misc/changelog.rst
@@ -36,6 +36,7 @@ Deprecations:
 Others:
 ^^^^^^^
 - Used issue forms instead of issue templates
+- Fixed flake8 config to be compatible with flake8 6+
 
 Documentation:
 ^^^^^^^^^^^^^^
diff --git a/setup.cfg b/setup.cfg
index b79e63a5d..5e307264f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -80,7 +80,8 @@ exclude = (?x)(
   )
 
 [flake8]
-ignore = W503,W504,E203,E231  # line breaks before and after binary operators
+# line breaks before and after binary operators
+ignore = W503,W504,E203,E231
 # Ignore import not used when aliases are defined
 per-file-ignores =
 	./stable_baselines3/__init__.py:F401
diff --git a/stable_baselines3/common/base_class.py b/stable_baselines3/common/base_class.py
index bb14f6ac9..9351bfb12 100644
--- a/stable_baselines3/common/base_class.py
+++ b/stable_baselines3/common/base_class.py
@@ -125,7 +125,7 @@ def __init__(
         # Used for computing fps, it is updated at each call of learn()
         self._num_timesteps_at_start = 0
         self.seed = seed
-        self.action_noise = None  # type: Optional[ActionNoise]
+        self.action_noise: Optional[ActionNoise] = None
         self.start_time = None
         self.policy = None
         self.learning_rate = learning_rate
diff --git a/tests/test_utils.py b/tests/test_utils.py
index e9281c363..e74b1d09e 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -298,13 +298,13 @@ def make_eval_env(with_monitor, wrapper_class=gym.Wrapper):
     episode_rewards, episode_lengths = evaluate_policy(
         model, eval_env, n_eval_episodes, return_episode_rewards=True, warn=False
     )
-    assert all(map(lambda l: l == 1, episode_lengths)), "AlwaysDoneWrapper did not fix episode lengths to one"
+    assert all(map(lambda length: length == 1, episode_lengths)), "AlwaysDoneWrapper did not fix episode lengths to one"
     eval_env.close()
 
     # Should get longer episodes with with Monitor (true episodes)
     eval_env = make_eval_env(with_monitor=True, wrapper_class=AlwaysDoneWrapper)
     episode_rewards, episode_lengths = evaluate_policy(model, eval_env, n_eval_episodes, return_episode_rewards=True)
-    assert all(map(lambda l: l > 1, episode_lengths)), "evaluate_policy did not get episode lengths from Monitor"
+    assert all(map(lambda length: length > 1, episode_lengths)), "evaluate_policy did not get episode lengths from Monitor"
     eval_env.close()