diff --git a/tox.ini b/tox.ini
index f4f351b..b99705f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -57,3 +57,16 @@ deps =
     ordereddict
     argparse
     coverage
+
+
+[testenv:pypy]
+# pypy can't be built with >3.4.4 so, in tox we pin back to the last
+# known good version of lxml
+deps =
+    setuptools
+    nose
+    mock
+    cssselect
+    cssutils
+    lxml==3.4.4
+    coverage