diff --git a/requirements/tools.txt b/requirements/tools.txt
index cbdebf8b5..0fd423ad2 100644
--- a/requirements/tools.txt
+++ b/requirements/tools.txt
@@ -1,3 +1,3 @@
 mypy==1.15.0
-flake8==7.1.2
+flake8==7.2.0
 black==24.8.0             # Until we drop Python 3.6 support, we have to stay with this version
diff --git a/slack_bolt/listener/thread_runner.py b/slack_bolt/listener/thread_runner.py
index 0b79c6ffd..c144daf1d 100644
--- a/slack_bolt/listener/thread_runner.py
+++ b/slack_bolt/listener/thread_runner.py
@@ -111,7 +111,7 @@ def run(
             if not request.lazy_only:
                 # start the listener function asynchronously
                 def run_ack_function_asynchronously():
-                    nonlocal ack, request, response
+                    nonlocal response
                     try:
                         self.listener_start_handler.handle(
                             request=request,