diff --git a/pytec/tec_qt.py b/pytec/tec_qt.py
index b97bca1..92d72eb 100755
--- a/pytec/tec_qt.py
+++ b/pytec/tec_qt.py
@@ -63,15 +63,16 @@ class MainWindow(QtWidgets.QMainWindow):
         self.thermostat = Thermostat(self, self.report_refresh_spin.value())
         self._connecting_task = None
 
-        def handle_connection_error():
+        @asyncSlot()
+        async def handle_connection_error():
             self.info_box.display_info_box(
                 "Connection Error", "Thermostat connection lost. Is it unplugged?"
             )
+            await self.thermostat.end_session()
 
         self.thermostat.connection_error.connect(handle_connection_error)
 
         self.thermostat.connection_error.connect(self.thermostat.timed_out)
-        self.thermostat.connection_error.connect(self.thermostat.end_session)
 
         self.thermostat.connection_state_changed.connect(self._on_connection_changed)