diff --git a/main.py b/main.py
index 510d08d..11a1b75 100644
--- a/main.py
+++ b/main.py
@@ -512,6 +512,7 @@ class ArduinoGUI:
         self.running = False
         if self.arduino:
             self.arduino.close()
+        self.communication_thread = None
         if self.ser:
             self.ser.close()
         self.root.quit()