diff --git a/tox.ini b/tox.ini
index 7b3b5b81..e5335e99 100644
--- a/tox.ini
+++ b/tox.ini
@@ -77,6 +77,7 @@ commands=
 
 [testenv:mypy]
 deps=
+    typing_extensions
     mypy
 commands=
     mypy tests/typing