2 files changed, 13 insertions, 2 deletions
diff --git a/setup.py b/setup.py
index ef10ca1..8879c5c 100644
--- a/setup.py
+++ b/setup.py
@@ -79,11 +79,12 @@ else:
     py_impl = getattr(platform, 'python_implementation', lambda: None)
     is_pypy = py_impl() == 'PyPy'
     is_jython = 'java' in sys.platform
+    is_pure = 'PURE_PYTHON' in os.environ
 
     # Jython cannot build the C optimizations, while on PyPy they are
     # anti-optimizations (the C extension compatibility layer is known-slow,
     # and defeats JIT opportunities).
-    if is_pypy or is_jython:
+    if is_pypy or is_jython or is_pure:
         features = {}
     else:
         features = {'codeoptimization': codeoptimization}
diff --git a/tox.ini b/tox.ini
index dd6591c..329acd8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py27,py33,py34,py35,pypy,pypy3,coverage,docs
+    py27,py27-pure,py33,py34,py34-pure,py35,pypy,pypy3,coverage,docs
 
 [testenv]
 commands =
@@ -8,6 +8,16 @@ commands =
 deps =
     zope.event
 
+[testenv:py27-pure]
+setenv =
+    PURE_PYTHON=1
+    PIP_CACHE_DIR = {envdir}/.cache
+
+[testenv:py34-pure]
+setenv =
+    PURE_PYTHON=1
+    PIP_CACHE_DIR = {envdir}/.cache
+
 [testenv:py]
 commands =
     python --version