diff --git a/requirements/tests.txt b/requirements/tests.txt
index 4239d4ef..65fd55fd 100644
--- a/requirements/tests.txt
+++ b/requirements/tests.txt
@@ -1,3 +1,3 @@
 pytest==3.0.2
 pytest-pep8==1.0.6
-mypy==0.630
+mypy==0.730
diff --git a/tox.ini b/tox.ini
index 9e8c8278..780c15ef 100644
--- a/tox.ini
+++ b/tox.ini
@@ -7,6 +7,7 @@
 envlist = {py35,py36,py37}-{tests,install},py36-docs
 
 [testenv]
+download = true
 # Make sure reading the UTF-8 from test.py works regardless of the locale used.
 setenv =
     LANG=C