diff --git a/python3/vimspector/stack_trace.py b/python3/vimspector/stack_trace.py
index e394df9..dd2662c 100644
--- a/python3/vimspector/stack_trace.py
+++ b/python3/vimspector/stack_trace.py
@@ -200,7 +200,7 @@ class StackTraceView( object ):
       self._requesting_threads = StackTraceView.ThreadRequestState.NO
       self._pending_thread_request = None
 
-      existing_threads = self._threads[:]
+      existing_threads = self._threads[ : ]
       self._threads.clear()
 
       if stopEvent is not None: