diff --git a/qt_helpers.py b/qt_helpers.py
index 5446ef4..828a61e 100644
--- a/qt_helpers.py
+++ b/qt_helpers.py
@@ -80,20 +80,16 @@ def is_pyqt5():
 is_pyqt = is_pyqt4
 QT_API_PYQT = QT_API_PYQT4
 
-_forbidden = set()
-
-
-def deny_module(module):
-    _forbidden.add(module)
-
 
 class ImportDenier(object):
     """
     Import hook to protect importing of both PySide and PyQt.
     """
 
+    _forbidden = set()
+
     def find_module(self, mod_name, pth):
-        if pth or not mod_name in _forbidden:
+        if pth or not mod_name in self._forbidden:
             return
         else:
             return self
@@ -102,6 +98,8 @@ def load_module(self, mod_name):
         raise ImportError("Importing %s forbidden by %s"
                           % (mod_name, __name__))
 
+    def deny_module(self, module):
+        self._forbidden.add(module)
 
 _import_hook = ImportDenier()
 sys.meta_path.append(_import_hook)
@@ -154,8 +152,8 @@ def _load_pyqt4():
     global QT_API
     QT_API = QT_API_PYQT4
 
-    deny_module('PySide')
-    deny_module('PyQt5')
+    _import_hook.deny_module('PySide')
+    _import_hook.deny_module('PyQt5')
 
 
 def _load_pyqt5():
@@ -185,8 +183,8 @@ def _load_pyqt5():
     global QT_API
     QT_API = QT_API_PYQT5
 
-    deny_module('PySide')
-    deny_module('PyQt4')
+    _import_hook.deny_module('PySide')
+    _import_hook.deny_module('PyQt4')
 
 
 def _load_pyside():
@@ -208,8 +206,8 @@ def setMargin(self, x):
     global QT_API
     QT_API = QT_API_PYSIDE
 
-    deny_module('PyQt4')
-    deny_module('PyQt5')
+    _import_hook.deny_module('PyQt4')
+    _import_hook.deny_module('PyQt5')
 
 
 QtCore = None
@@ -227,7 +225,14 @@ def reload_qt():
     e.g. PySide if PyQt4 is loaded).
     """
 
-    _forbidden.clear()
+    # Clear any forbidden modules
+    _import_hook._forbidden.clear()
+
+    # Quit app if active
+    global qapp
+    if qapp is not None:
+        qapp.quit()
+        qapp = None
 
     global QtCore
     global QtGui
@@ -298,7 +303,10 @@ def _load_ui_pyqt5(path, parent):
     return loadUi(path, parent)
 
 
+qapp = None
+
 def get_qapp(icon_path=None):
+    global qapp
     qapp = QtGui.QApplication.instance()
     if qapp is None:
         qapp = QtGui.QApplication([''])
diff --git a/test_switch.py b/test_switch.py
index b59a8e4..57b0275 100644
--- a/test_switch.py
+++ b/test_switch.py
@@ -13,12 +13,12 @@
 class TestQT(object):
 
     def teardown_class(cls):
-        for m in sys.modules.keys():
+        for m in list(sys.modules.keys()):
             if m.startswith('PyQt4') or m.startswith('PySide'):
                 sys.modules.pop(m)
 
     def setup_method(self, method):
-        qt.deny_module(None)
+        qt._import_hook.deny_module(None)
         if 'QT_API' in os.environ:
             os.environ.pop('QT_API')
 
@@ -62,16 +62,13 @@ def test_load_ui_qt4(self):
         app = get_qapp()
         load_ui('test.ui')
         app.quit()
-        del app
 
     def test_load_ui_pyside(self):
         self._load_pyside()
         from qt_helpers import load_ui, get_qapp
         app = get_qapp()
         load_ui('test.ui')
-        app.exit()
         app.quit()
-        del app
 
     def test_submodule_import(self):
         self._load_qt4()
@@ -140,8 +137,6 @@ def test_launch_after_reload(self):
         time.sleep(0.1)
         app.quit()
 
-        del app
-
         os.environ['QT_API'] = qt.QT_API_PYQT4
         qt.reload_qt()
 
@@ -155,8 +150,6 @@ def test_launch_after_reload(self):
         time.sleep(0.1)
         app.quit()
 
-        del app
-
         os.environ['QT_API'] = qt.QT_API_PYSIDE
         qt.reload_qt()
 
@@ -169,5 +162,3 @@ def test_launch_after_reload(self):
         app.flush()
         time.sleep(0.1)
         app.quit()
-
-        del app