diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 51e9cff..37bba23 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -13,18 +13,40 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: ['2.7', 'pypy-2.7', '3.9', '3.10', '3.11']
+        python-version: ['pypy-2.7', '3.9', '3.10', '3.11']
         exclude:
           - os: macos-latest
             python-version: 'pypy-2.7'
+          - os: windows-latest
+            python-version: 'pypy-2.7'
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      - name: Install dependencies
+        run: |
+          python -m pip install wheel
+      - name: Install
+        shell: bash
+        run: |
+          SCANDIR_REQUIRE_C_EXTENSION=1 python -m pip -v install .
+      - name: Run tests
+        run: |
+          python test/run_tests.py
+  build27:
+    runs-on: ubuntu-latest
+    container:
+      image: python:2.7.18-buster
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install dependencies
+        run: |
+          python -m pip install wheel
+      - name: Install
+        run: |
+          SCANDIR_REQUIRE_C_EXTENSION=1 python -m pip -v install .
       - name: Run tests
         run: |
-          python --version
-          python setup.py install
           python test/run_tests.py
diff --git a/setup.py b/setup.py
index fded786..e90c8c6 100644
--- a/setup.py
+++ b/setup.py
@@ -17,6 +17,8 @@
 import sys
 import logging
 
+require_c_extension = bool(os.environ.get('SCANDIR_REQUIRE_C_EXTENSION'))
+
 # Get version without importing scandir because that will lock the
 # .pyd file (if scandir is already installed) so it can't be
 # overwritten during the install process
@@ -42,10 +44,13 @@ def build_extension(self, ext):
         try:
             base_build_ext.build_extension(self, ext)
         except Exception:
+            if require_c_extension:
+                logging.error('SCANDIR_REQUIRE_C_EXTENSION is set, not falling back to Python implementation')
+                raise
             info = sys.exc_info()
             logging.warn("building %s failed with %s: %s", ext.name, info[0], info[1])
 
-extension = Extension('_scandir', ['_scandir.c'], optional=True)
+extension = Extension('_scandir', ['_scandir.c'], optional=not require_c_extension)
 
 
 setup(