diff --git a/freqtrade/persistence/pairlock_middleware.py b/freqtrade/persistence/pairlock_middleware.py
index ec57e91fc..69d8b098b 100644
--- a/freqtrade/persistence/pairlock_middleware.py
+++ b/freqtrade/persistence/pairlock_middleware.py
@@ -87,7 +87,7 @@ class PairLocks():
         Get the lock that expires the latest for the pair given.
         """
         locks = PairLocks.get_pair_locks(pair, now, side=side)
-        locks = sorted(locks, key=lambda l: l.lock_end_time, reverse=True)
+        locks = sorted(locks, key=lambda lock: lock.lock_end_time, reverse=True)
         return locks[0] if locks else None
 
     @staticmethod
diff --git a/requirements-dev.txt b/requirements-dev.txt
index b46c244b5..ffce3d696 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -7,7 +7,7 @@
 -r docs/requirements-docs.txt
 
 coveralls==3.3.1
-flake8==5.0.4
+flake8==6.0.0
 flake8-tidy-imports==4.8.0
 mypy==0.991
 pre-commit==2.20.0