diff --git a/tox.ini b/tox.ini
index bda6963b..e4093c99 100644
--- a/tox.ini
+++ b/tox.ini
@@ -23,6 +23,8 @@ setenv =
     env36: JEDI_TEST_ENVIRONMENT=36
     env37: JEDI_TEST_ENVIRONMENT=37
 commands =
+# Overwrite the parso version.
+    pip install git+https://github.com/davidhalter/parso.git
     py.test {posargs:jedi test}
 [testenv:py27]
 deps =