diff --git a/source/ipi/tests/test_driver.py b/source/ipi/tests/test_driver.py
index 20e721f686..b0fbf53b01 100644
--- a/source/ipi/tests/test_driver.py
+++ b/source/ipi/tests/test_driver.py
@@ -261,6 +261,7 @@ def setUpClass(cls):
     def setUp(self):
         super().setUp()
 
+        self.box = np.array([13.0, 0.0, 0.0, 0.0, 13.0, 0.0, 0.0, 0.0, 13.0])
         self.expected_e = np.array(
             [
                 -93.016873944029,