diff --git a/tox.ini b/tox.ini
index c943243656..2050647a63 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,7 +11,7 @@ requires = pip >= 19.0.0
 deps =
     setuptools
     pre-commit
-    numpy>=1.9
+    numpy>=1.9,<2
     pytest
     PyYAML
     tables