diff --git a/tests/test_io.py b/tests/test_io.py
index cf7f569a..a95552b8 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -59,7 +59,7 @@ def test_read_mrc_meta_data(self):
         self.assertIn("make sure this is correct", cm.output[0])
 
     def test_half_precision_read_write_cycle(self):
-        array = np.random.rand((3, 3, 3)).astype(np.float16)
+        array = np.random.rand(27).reshape((3, 3, 3)).astype(np.float16)
         fname = pathlib.Path(self.tempdirname) / "test_half.mrc"
         # Make sure no warnings are raised
         with self.assertNoLogs(level="WARNING"):