diff --git a/tox.ini b/tox.ini
index 7d5ce1b..80db26d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,7 @@ envlist = py27,py34,py35,py36,py37
 deps =
     futures
     SQLAlchemy>=1.0.0, <2.0.0
+    numpy>=1.6
     pytest>=3.5
     pytest-cov
     pytest-flake8>=1.0.1