diff --git a/timebot/gui.py b/timebot/gui.py
index 4def9a3..cd4ca06 100644
--- a/timebot/gui.py
+++ b/timebot/gui.py
@@ -130,7 +130,7 @@ class TimebotMainWindow(QWidget):
         self.btn_update_status.setText("Refresh Status")
         self.update_status_running = False
 
-    def update_hours_present(self, override=None):
+    def update_hours_present(self, override: datetime.timedelta = None):
         if override is not None:
             self.hours_present: datetime.timedelta = override
         elif self.hours_present > datetime.timedelta(seconds=self.main_window_timer_time / 100):