diff --git a/tox.ini b/tox.ini
index 7121df049..034d89372 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,5 +34,6 @@ commands =
 skip_install = true
 deps =
     mypy==1.7.1
+    numpy
 commands =
     mypy src {posargs}