diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index abd0a0d..c32298d 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -6,7 +6,7 @@ on:
 jobs:
   inspect:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     steps:
       - uses: actions/checkout@v2
         with:
@@ -37,7 +37,7 @@ jobs:
           prerelease: false
   pypi_release:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     needs:
       - inspect
       - github_release
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index a72f8ed..a099ed6 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -6,7 +6,7 @@ on:
 jobs:
   tests:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     steps:
       - uses: actions/checkout@v2
       - name: Install package.
@@ -17,7 +17,7 @@ jobs:
         run: pytest
   build:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     steps:
       - uses: actions/checkout@v2
       - name: Install package.
@@ -26,7 +26,7 @@ jobs:
         run: aip-site-gen tests/test_data/ /out/
   lint:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     steps:
       - uses: actions/checkout@v2
       - name: Install the linter (flake8).
@@ -35,9 +35,11 @@ jobs:
         run: flake8 aip_site/ tests/
   mypy:
     runs-on: ubuntu-latest
-    container: python:3.8
+    container: python:3.9
     steps:
       - uses: actions/checkout@v2
+      - name: Install package.
+        run: pip install .
       - name: Install mypy.
         run: pip install mypy
       - name: Run mypy.
diff --git a/aip_site/jinja/loaders.py b/aip_site/jinja/loaders.py
index 9443373..b8d9cae 100644
--- a/aip_site/jinja/loaders.py
+++ b/aip_site/jinja/loaders.py
@@ -74,7 +74,7 @@ def get_source(self, env, template: str) -> typing.Tuple[str, str, None]:
         # Return the template information.
         return contents, fn, None
 
-    def list_templates(self) -> typing.Sequence[str]:
+    def list_templates(self) -> typing.List[str]:
         answer = []
 
         # We sort the files in the directory to read more specific
diff --git a/setup.py b/setup.py
index 928602d..e5fc1dc 100644
--- a/setup.py
+++ b/setup.py
@@ -55,6 +55,8 @@
         'pyscss==1.3.7',
         'pyyaml==5.4.1',
         'six==1.16.0',
+        'types-Markdown==3.3.15',
+        'types-PyYAML==6.0.7',
         'werkzeug==2.0.1',
     ),
     python_requires='>=3.8',