diff --git a/noisicaa/ui/graph/canvas_test.py b/noisicaa/ui/graph/canvas_test.py
index 88970237..8797a2ea 100644
--- a/noisicaa/ui/graph/canvas_test.py
+++ b/noisicaa/ui/graph/canvas_test.py
@@ -49,8 +49,8 @@ class CanvasTest(uitest.ProjectMixin, uitest.UITestCase):
         self.canvas.zoomStarted.connect(sig)
 
         evt = QtGui.QWheelEvent(
-            QtCore.QPointF(200, 100),
-            QtCore.QPointF(500, 300),
+            QtCore.QPoint(200, 100),
+            QtCore.QPoint(500, 300),
             QtCore.QPoint(0, 10),
             QtCore.QPoint(0, 120),
             10, Qt.Vertical,
@@ -69,8 +69,8 @@ class CanvasTest(uitest.ProjectMixin, uitest.UITestCase):
         self.canvas.zoomStarted.connect(sig)
 
         evt = QtGui.QWheelEvent(
-            QtCore.QPointF(200, 100),
-            QtCore.QPointF(500, 300),
+            QtCore.QPoint(200, 100),
+            QtCore.QPoint(500, 300),
             QtCore.QPoint(0, -10),
             QtCore.QPoint(0, -120),
             10, Qt.Vertical,
diff --git a/noisicaa/ui/property_connector.py b/noisicaa/ui/property_connector.py
index 5d15f453..dfc0700f 100644
--- a/noisicaa/ui/property_connector.py
+++ b/noisicaa/ui/property_connector.py
@@ -89,8 +89,8 @@ class QComboBoxConnector(Generic[V], PropertyConnector[V, QtWidgets.QComboBox]):
         idx = self._widget.findData(self.value())
         if idx >= 0:
             self._widget.setCurrentIndex(idx)
-        connection = self._widget.currentIndexChanged.connect(self._widgetChanged)
-        self.add_cleanup_function(lambda: self._widget.currentIndexChanged.disconnect(connection))
+        self._widget.currentIndexChanged.connect(self._widgetChanged)
+        self.add_cleanup_function(lambda: self._widget.currentIndexChanged.disconnect(self._widgetChanged))
 
     def _widgetChanged(self) -> None:
         self.setValue(self._widget.currentData())
@@ -141,8 +141,8 @@ class QDoubleSpinBoxConnector(PropertyConnector[float, QtWidgets.QDoubleSpinBox]
 
     def _connectToWidget(self) -> None:
         self._widget.setValue(self.value())
-        connection = self._widget.valueChanged.connect(self.__valueChanged)
-        self.add_cleanup_function(lambda: self._widget.valueChanged.disconnect(connection))
+        self._widget.valueChanged.connect(self.__valueChanged)
+        self.add_cleanup_function(lambda: self._widget.valueChanged.disconnect(self.__valueChanged))
 
     def __valueChanged(self, value: float) -> None:
         if self.__ignore_change:
diff --git a/noisicaa/ui/settings_dialog.py b/noisicaa/ui/settings_dialog.py
index 38a4c479..df5ae809 100644
--- a/noisicaa/ui/settings_dialog.py
+++ b/noisicaa/ui/settings_dialog.py
@@ -59,7 +59,7 @@ class SettingsDialog(ui_base.CommonMixin, QtWidgets.QDialog):
         # TODO: somehow always ends up being shown...
         #self.setVisible(bool(self.app.settings.value('dialog/settings/visible', False)))
         self.restoreGeometry(self.app.settings.value('dialog/settings/geometry', b''))
-        self.tabs.setCurrentIndex(int(self.app.settings.value('dialog/settings/page', 0)))
+        self.tabs.setCurrentIndex(int(self.app.settings.value('dialog/settings/page') or 0))
 
     def storeState(self) -> None:
         s = self.app.settings
diff --git a/noisicaa/ui/stat_monitor.py b/noisicaa/ui/stat_monitor.py
index 837d9f5a..0ecb6896 100644
--- a/noisicaa/ui/stat_monitor.py
+++ b/noisicaa/ui/stat_monitor.py
@@ -223,8 +223,7 @@ class StatMonitor(ui_base.AbstractStatMonitor):
         self.setCentralWidget(main_widget)
 
         self.setVisible(
-            int(self.app.settings.value(
-                'dialog/stat_monitor/visible', False)))
+            bool(self.app.settings.value('dialog/stat_monitor/visible') or False))
         self.restoreGeometry(
             self.app.settings.value(
                 'dialog/stat_monitor/geometry', b''))
diff --git a/noisidev/qttest.py b/noisidev/qttest.py
index 63cb05b6..ad4dcc80 100644
--- a/noisidev/qttest.py
+++ b/noisidev/qttest.py
@@ -33,24 +33,33 @@ from . import unittest
 logger = logging.getLogger(__name__)
 
 
+qt_app = None
+
+
 class QtTestCase(unittest.AsyncTestCase):
     use_default_loop = True
-    qt_app = None  # type: QtWidgets.QApplication
+    qt_app = None
 
     @classmethod
     def setUpClass(cls):
         if not constants.TEST_OPTS.ALLOW_UI:
             return
 
-        if cls.qt_app is None:
-            cls.qt_app = QtWidgets.QApplication(['unittest'])
-            cls.qt_app.setQuitOnLastWindowClosed(False)
+        global qt_app
+        if qt_app is None:
+            qt_app = QtWidgets.QApplication(['unittest'])
+            qt_app.setQuitOnLastWindowClosed(False)
+        cls.qt_app = qt_app
 
         event_loop = quamash.QEventLoop(cls.qt_app)
         asyncio.set_event_loop(event_loop)
         executor = concurrent.futures.ThreadPoolExecutor(max_workers=10)
         event_loop.set_default_executor(executor)
 
+    @classmethod
+    def tearDownClass(cls):
+        cls.qt_app = None
+
     def setup_testcase(self):
         if not constants.TEST_OPTS.ALLOW_UI:
             raise unittest.SkipTest("QT tests disabled")