diff --git a/.github/workflows/run-tests-workflow.yml b/.github/workflows/run-tests-workflow.yml
index 37c1fbad..800784e9 100644
--- a/.github/workflows/run-tests-workflow.yml
+++ b/.github/workflows/run-tests-workflow.yml
@@ -17,10 +17,6 @@ jobs:
       matrix:
         include:
           # Linux
-          - os: ubuntu-20.04
-            python-version: 3.7
-            test-env: "PyQt5~=5.9.2 qasync<0.19.0"
-
           - os: ubuntu-20.04
             python-version: 3.8
             test-env: "PyQt5~=5.12.0"
@@ -54,6 +50,10 @@ jobs:
             test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
             extra-system-packages: "glibc-tools"
 
+          - os: ubuntu-22.04
+            python-version: "3.12"
+            test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
+            extra-system-packages: "glibc-tools"
 
           # macOS
           - os: macos-11
@@ -80,11 +80,11 @@ jobs:
             python-version: "3.11"
             test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
 
-          # Windows
-          - os: windows-2019
-            python-version: 3.7
-            test-env: "PyQt5~=5.9.2"
+          - os: macos-12
+            python-version: "3.12"
+            test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
 
+          # Windows
           - os: windows-2019
             python-version: 3.8
             test-env: "PyQt5~=5.12.0"
@@ -109,6 +109,10 @@ jobs:
             python-version: "3.11"
             test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
 
+          - os: windows-2019
+            python-version: "3.12"
+            test-env: "PyQt6~=6.5.0 PyQt6-Qt6~=6.5.0"
+
     steps:
       - uses: actions/checkout@v3
       - name: Setup Python
diff --git a/orangecanvas/application/tests/test_main.py b/orangecanvas/application/tests/test_main.py
index 2648bfbb..927375e8 100644
--- a/orangecanvas/application/tests/test_main.py
+++ b/orangecanvas/application/tests/test_main.py
@@ -123,7 +123,7 @@ def test_run(self):
         self.assertEqual(res, 42)
 
     @with_patched_main_application
-    def test_run(self):
+    def test_run_with_file(self):
         m = Main()
         with patch.object(self.app, "exec", lambda: 42), \
              patch.object(CanvasMainWindow, "open_scheme_file", Mock()), \
diff --git a/orangecanvas/gui/windowlistmanager.py b/orangecanvas/gui/windowlistmanager.py
index 727100ef..6f173faf 100644
--- a/orangecanvas/gui/windowlistmanager.py
+++ b/orangecanvas/gui/windowlistmanager.py
@@ -33,8 +33,8 @@ def instance() -> "WindowListManager":
     def __init__(self, *args, **kwargs):
         if self.__instance is not None:
             raise RuntimeError
-        WindowListManager.__instance = self
         super().__init__(*args, **kwargs)
+        WindowListManager.__instance = self
         self.__group = QActionGroup(
             self, objectName="window-list-manager-action-group"
         )