diff --git a/.github/workflows/CI.yaml b/.github/workflows/CI.yaml
index e31b1b82..88871056 100644
--- a/.github/workflows/CI.yaml
+++ b/.github/workflows/CI.yaml
@@ -10,12 +10,12 @@ jobs:
     # https://github.com/actions/python-versions/blob/main/versions-manifest.json
     strategy:
       matrix:
-        os: [macos-latest, ubuntu-20.04]
-        python-version: [3.8, 3.11, pypy-3.8, pypy-3.10]
+        os: [macos-latest, ubuntu-latest]
+        python-version: ['3.11', 'pypy-3.8', 'pypy-3.10']
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Setup Python environment
-        uses: actions/setup-python@v2.2.1
+        uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install Requirements
@@ -33,7 +33,7 @@ jobs:
         run: |
           pytest
       - name: Run MyPy
-        if: matrix.python-version != 'pypy-3.7' 
+        if: ${{ !startsWith(matrix.python-version, 'pypy') }}
         run: |
           pip install enum34 mypy types-six
           ./mypy-run.sh
diff --git a/.github/workflows/coverage.yaml b/.github/workflows/coverage.yaml
index d01071b8..9b1aaab0 100644
--- a/.github/workflows/coverage.yaml
+++ b/.github/workflows/coverage.yaml
@@ -11,11 +11,11 @@ jobs:
   Coverage:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Setup Python environment
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
-          python-version: '3.9'
+          python-version: '3.11'
       - name: Setup virtual environment
         run: |
           python -m venv venv
@@ -31,6 +31,6 @@ jobs:
           coverage run --rcfile=.coveragerc -m pytest
           coverage xml
       - name: Publish Coverage
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v5
         with:
           flags: unit
diff --git a/stone/backend.py b/stone/backend.py
index b7eacc83..24ccf5b8 100644
--- a/stone/backend.py
+++ b/stone/backend.py
@@ -89,7 +89,7 @@ class to be recognized as such.
     tabs_for_indents = False
 
     # Can be overridden with an argparse.ArgumentParser object.
-    cmdline_parser = None  # type: argparse.ArgumentParser
+    cmdline_parser = None  # type: typing.Optional[argparse.ArgumentParser]
 
     # Can be overridden by a subclass. If true, stone.data_type.Alias
     # objects will be present in the API object. If false, aliases are masked