diff --git a/pytec/tec_qt.py b/pytec/tec_qt.py
index 8447d12..b395f52 100755
--- a/pytec/tec_qt.py
+++ b/pytec/tec_qt.py
@@ -65,11 +65,12 @@ class MainWindow(QtWidgets.QMainWindow):
         )
         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?"
             )
-            self.thermostat.end_session()
+            await self.thermostat.end_session()
 
         self.thermostat.connection_error.connect(handle_connection_error)