diff --git a/src/AccessControl/ImplPython.py b/src/AccessControl/ImplPython.py
index 61fd120..2a07365 100644
--- a/src/AccessControl/ImplPython.py
+++ b/src/AccessControl/ImplPython.py
@@ -31,7 +31,7 @@
 # security implementations exist, we can switch between them later.
 try:
     from AccessControl.cAccessControl import _what_not_even_god_should_do
-except ImportError:
+except (ImportError, AttributeError):
     _what_not_even_god_should_do = []
 
 from AccessControl.interfaces import ISecurityManager
diff --git a/src/AccessControl/tests/testSecurityManager.py b/src/AccessControl/tests/testSecurityManager.py
index 40058a0..1f04577 100644
--- a/src/AccessControl/tests/testSecurityManager.py
+++ b/src/AccessControl/tests/testSecurityManager.py
@@ -15,7 +15,7 @@
 """
 
 import unittest
-
+import os
 
 _THREAD_ID = 123
 
@@ -250,6 +250,7 @@ def _getTargetClass(self):
         return SecurityManager
 
 
+@unittest.skipIf(os.environ.get('PURE_PYTHON'), 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 c81face..cddece6 100644
--- a/src/AccessControl/tests/testZopeSecurityPolicy.py
+++ b/src/AccessControl/tests/testZopeSecurityPolicy.py
@@ -12,6 +12,7 @@
 ##############################################################################
 
 import sys
+import os
 import unittest
 from doctest import DocTestSuite
 
@@ -775,9 +776,10 @@ def loop():
 def test_suite():
     suite = unittest.TestSuite()
     suite.addTest(unittest.makeSuite(Python_ZSPTests))
-    suite.addTest(unittest.makeSuite(C_ZSPTests))
     suite.addTest(unittest.makeSuite(Python_SMTests))
-    suite.addTest(unittest.makeSuite(C_SMTests))
+    if not os.environ.get('PURE_PYTHON'):
+        suite.addTest(unittest.makeSuite(C_ZSPTests))
+        suite.addTest(unittest.makeSuite(C_SMTests))
     suite.addTest(DocTestSuite())
     suite.addTest(unittest.makeSuite(GetRolesWithMultiThreadTest))
     return suite
diff --git a/tox.ini b/tox.ini
index 079a38c..3ea6fcf 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,6 +19,9 @@ deps =
     setuptools < 52
     zc.buildout
 skip_install = true
+setenv =
+    PURE_PYTHON=1
+    AC_PURE_PYTHON=1
 
 [testenv:coverage]
 basepython = python3