1 files changed, 1 insertions, 0 deletions

diff --git a/setup.py b/setup.py
index 088d5b8e7..a427d5493 100644
--- a/setup.py
+++ b/setup.py
@@ -52,6 +52,7 @@ extras_require = {
         'pytest-cov',
         'html5lib',
         'typed_ast',  # for py35-37
+        'cython',
     ],
 }