diff --git a/tox.ini b/tox.ini
index f80d268..6a60800 100644
--- a/tox.ini
+++ b/tox.ini
@@ -56,6 +56,7 @@ deps = mypy
        types-appdirs
        types-Pillow
        types-pyserial
+       types-pywin32
        hypothesis>=6.83
        jaconv
 commands = mypy src test