diff --git a/tox.ini b/tox.ini
index 26d80d2..926fe1f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,5 +21,6 @@ deps =
   httmock
   requests-mock
   ipdb
+  xmlschema<1.1
 commands =
   django111: py.test {posargs: --junitxml=test_{envname}_results.xml tests/}