diff --git a/PySubtitleGPT/SubtitleProject.py b/PySubtitleGPT/SubtitleProject.py
index b54eae1f..c175247c 100644
--- a/PySubtitleGPT/SubtitleProject.py
+++ b/PySubtitleGPT/SubtitleProject.py
@@ -21,6 +21,7 @@ def __init__(self, options : Options):
         self.projectfile = None
         self.needsupdate = False
         self.lock = threading.Lock()
+        self.stop_event = None
         
         project_mode = self.options.get('project', '')
         if project_mode: