diff --git a/tox.ini b/tox.ini
index 038a63247..3cef5a268 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 downloadcache = {toxworkdir}/cache/
-envlist = py27, pypy
+envlist = py27, pypy, py27-noext, pypy-noext
 
 [testenv]
 deps =
@@ -18,3 +18,9 @@ setenv =
 [testenv:py25]
 setenv =
     PIP_INSECURE=1
+
+[testenv:py27-noext]
+commands = make check-noextensions
+
+[testenv:pypy-noext]
+commands = make check-noextensions