diff --git a/CHANGES.rst b/CHANGES.rst
index 467d54c..8423844 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -6,6 +6,8 @@ For changes before version 3.0, see ``HISTORY.rst``.
 7.1 (unreleased)
 ----------------
 
+- Understand ``PURE_PYTHON`` environment variable set to ``0``.
+
 
 7.0 (2024-05-30)
 ----------------
diff --git a/src/AccessControl/tests/testSecurityManager.py b/src/AccessControl/tests/testSecurityManager.py
index 5a86d5d..f506017 100644
--- a/src/AccessControl/tests/testSecurityManager.py
+++ b/src/AccessControl/tests/testSecurityManager.py
@@ -251,7 +251,7 @@ def _getTargetClass(self):
         return SecurityManager
 
 
-@unittest.skipIf(os.environ.get('PURE_PYTHON'), reason="Test expects C impl.")
+@unittest.skipIf(int(os.environ.get('PURE_PYTHON', '0')), reason="Test expects C impl.")
 class C_SecurityManagerTests(SecurityManagerTestBase,
                              ISecurityManagerConformance,
                              unittest.TestCase):
diff --git a/src/AccessControl/tests/testZopeSecurityPolicy.py b/src/AccessControl/tests/testZopeSecurityPolicy.py
index 9b12a0f..103f948 100644
--- a/src/AccessControl/tests/testZopeSecurityPolicy.py
+++ b/src/AccessControl/tests/testZopeSecurityPolicy.py
@@ -772,7 +772,7 @@ def test_suite():
         unittest.defaultTestLoader.loadTestsFromTestCase(Python_ZSPTests))
     suite.addTest(
         unittest.defaultTestLoader.loadTestsFromTestCase(Python_SMTests))
-    if not os.environ.get('PURE_PYTHON'):
+    if not int(os.environ.get('PURE_PYTHON', '0')):
         suite.addTest(
             unittest.defaultTestLoader.loadTestsFromTestCase(C_ZSPTests))
         suite.addTest(