diff --git a/tox.ini b/tox.ini
index 9521603..bc2217e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -38,6 +38,7 @@ deps =
   pylint<1.8
   pylint-django<0.8.1
   django-webtest<1.9.3
+  xmlschema<1.1
 commands =
   py.test {env:COVERAGE:} {posargs:tests/}
   pylint: ./pylint.sh atreal_openads/